Introduction
I bought both the Dolphin Proteus DX3 and the Dolphin Sigma with my own money and ran them side by side in my pool for a full season. This isn't a spec-sheet showdown. It's what I actually saw after months of dropping each one in the water and watching where it went, what it missed, and what drove me nuts.
Here's the short version on the Proteus DX3: it's a solid entry-level cleaner. Floor and wall coverage held up run after run, and I never worried it would leave a mess on the bottom. But two things bugged me. It has no NanoFilters, and it doesn't touch the waterline. There's also a restocking fee tucked into the fine print that a lot of buyers won't see coming, and I think you deserve to know about it before you click buy.
The Sigma plays a completely different game. It's built on Maytronics' commercial platform, and you feel that the second it starts working. Waterline cleaning, a gyroscope for real navigation, and full Wi-Fi app control put it near the top of anything I've tested. Yes, it costs more. But you're paying for a machine that cleans the whole pool, not just the parts that are easy to reach.
"The Sigma is a commercial cleaner that happens to fit in a backyard pool."
I put both robots through the same checks: how much of the pool they actually reached, how well they trapped debris, and what living with them day to day felt like. The DX3 gives you a programmable timer and genuinely strong vacuum pull. Where it stops short is the complete clean, and that comes down to no NanoFilters and no waterline work.
Between its two filter options and the myDolphin Plus app, the Sigma earns its spot as the advanced pick here. A three-year warranty, the gyroscope, and Hypergrip tracks aren't marketing fluff. In my testing they translated into a robot that handles heavy debris loads without needing me to babysit it.
"If you want the best pool in the neighborhood, the Sigma gets you there."
So where does that leave you? The Proteus DX3 is dependable and does its core job well, but the Sigma simply cleans more of your pool and gives you more to work with. Figure out what your pool actually needs. If you want the most complete, hands-off clean I tested, the Sigma is the one I'd hand you.
How We Test
I don't do quick weekend impressions. Every robot I review lives in my pool for roughly three months so I can see how it holds up once the novelty wears off and real debris starts piling in. That's the only way I've found to tell you something true about how a cleaner performs, not just how it demos.
Coverage is where I always start. I watch each robot run cycle after cycle and track exactly where it goes: the floor, up the walls, and whether it ever reaches the waterline. The Dolphin Proteus DX3 was steady on the floor and climbed walls fine, but the waterline stayed dirty. It just doesn't clean up there, and after a few weeks I could see the scum line building.
The Dolphin Sigma was a different story. With dual scrubbing brushes, Hypergrip tracks, and a gyroscope guiding it, it covered the whole pool and got right up to the waterline every run. A lot of cleaners quietly skip that zone. The Sigma didn't.
"The Sigma cleaned corners of my pool other robots pretended weren't there."
Filtration is the next thing I test, because a robot that stirs up debris without trapping it isn't helping anyone. I run each one against fine silt and bigger stuff like leaves. The Proteus DX3 uses a standard fine filter. It grabs the everyday debris fine, but it can't match what NanoFilters pull out of the water.
The Sigma ships with both a standard filter and an ultrafine option. Swapping to the ultrafine setup, I watched the water get noticeably clearer because it was pulling out particles the standard filter let slip by. That dual system is a real advantage when you care about clarity, not just the big debris.
"Fine silt that clouded my water disappeared once I ran the Sigma's ultrafine filters."
Last, I dig into features and warranty, because that's what you live with long-term. On the DX3, the programmable timer was a nice touch and worked reliably. What I didn't love: that hidden restocking fee, which is a real gotcha if you ever need to return it, plus there's no proper handle, so hauling the wet robot out was more awkward than it should be.
The Sigma answers most of that with Wi-Fi and the myDolphin Plus app. I scheduled cleanings from my phone, kicked off cycles from the couch, and never touched a physical timer. Back it with a three-year warranty and you've got a robot built to last, not just to impress on day one.
"Running the Sigma from my phone made the DX3's timer feel a generation behind."
This is the process behind every verdict I give you: months in the water, the same tests, and honest notes on both the good and the annoying. The Sigma came out as the standout on features and thoroughness. The Proteus DX3 is a genuinely solid cleaner that just falls short in a few spots that matter.
Both robots earned their time in my pool, and I based every call here on what they actually did over weeks, not a single lucky run. If you want to see how these two stack up against everything else I've tested, my best pool robots page has the full shortlist.
Coverage
The Proteus DX3 is rated for inground pools up to 33 feet, and it cleans the floor and walls without complaint. What it won't do is the waterline. For an inground pool that's a real gap, because the waterline is where the scum ring forms, and if the robot skips it, you're the one scrubbing it by hand.
The Sigma is the opposite. It cleans the floor and walls, and it keeps climbing right up to the waterline thanks to the gyroscope and dual stabilizer keeping it steady up there. That's the difference between a pool that's mostly clean and one that's actually clean, with no algae ring waiting for you at the surface.
"The Sigma cleaned corners of my pool other robots pretended weren't there."
Both are reliable at what they do, but the coverage gap is obvious once you watch them run. The DX3 handles the floor and walls efficiently and leaves your pool cleaner than it was. It just hands you a little homework at the waterline every week.
The Sigma's full coverage, waterline included, is what really separates it. Between the dual scrubbing brushes, Hypergrip tracks, and gyroscopic navigation, it gives you a genuinely hands-off clean. If your goal is the least effort for the cleanest result, that combination is hard to beat.
"If you want the best pool in the neighborhood, the Sigma gets you there."
The scores line up with what I saw. The Proteus DX3 earned a respectable 8/10 for coverage, which is a good number for an entry-level unit. The Sigma pulled a perfect 10/10, and it earned it by cleaning the floor, the walls, and the waterline instead of tapping out at two of the three.
On coverage alone, the Sigma is the clear winner. It cleans the entire pool in a way the Proteus DX3 just can't. If you want the most automated, thorough clean of these two, the Sigma is the one I'd point you toward.
Want to see how both of these rank against the rest? My best pool robots page lays out the top-rated cleaners I've tested so you can pick with your eyes open.
Filters
Filters are where these two really split apart. Comparing the systems in the Dolphin Proteus DX3 and the Dolphin Sigma side by side, the difference in what each one traps is easy to see, and it changes how your water looks.
The Proteus DX3 runs a standard fine filter. For the everyday stuff, dirt, small leaves, the odd bug, it does the job. Where it struggles is the fine particles, the tiny bits that keep water looking hazy instead of clear. If a genuinely clear pool is what you're after, that's a limitation you'll notice.
The Sigma gives you both a standard filter and an ultrafine one. That dual system is the whole story here. It handles the big debris and then goes after the microscopic particles the DX3 leaves behind. The ultrafine NanoFilters are the reason my water looked polished instead of just picked up.
"Fine silt that clouded my water disappeared once I ran the Sigma's ultrafine filters."
Given the choice, I ran the Sigma's filters over the DX3's every time. Being able to switch between standard and ultrafine meant I could match the filter to whatever the pool needed that week, heavy leaves one day, fine dust the next. That flexibility is what keeps the water clear no matter what blows in.
The DX3's standard filter is fine for typical debris but can't touch the fine stuff. The Sigma's ultrafine filters are exactly where it pulls ahead, and that makes it the pick for anyone who cares about how clear the water actually looks, not just whether the leaves are gone.
"When clarity matters, nothing here touches the Sigma."
The numbers back it up. The Proteus DX3 landed a filter score of 6, which is fair for a basic, dependable setup. The Sigma earned a 9.4, and that gap is the difference between a filter that catches debris and one that keeps your water genuinely clear.
Bottom line on filtration: the Sigma wins this one clearly. If the cleanest possible water is your goal, its dual filter system is the tool for the job. The Proteus DX3 will keep your pool tidy, but the Sigma is the one that makes it look great.
Feature Set
Line up the feature sets of the Dolphin Proteus DX3 and the Dolphin Sigma and the gap gets wide fast. It shows up in what each one can do, how easy it is to live with, and how it feels in your hand.
The Proteus DX3 gives you a programmable timer, so you can set it to run every day, every other day, or every three days. Handy, sure, but that's table stakes at this point, and it's a long way from the connected control you get on nicer models. The missing handle is the other catch. Moving and hauling the robot around was more of a hassle than it should have been.
The Sigma comes at it from a completely different level, with a Wi-Fi app and a three-year warranty behind it. The myDolphin Plus app lets you schedule cleanings, drive the robot manually, and tweak cleaning cycles right from your phone. That kind of control is exactly where the Sigma pulls away.
"Running the Sigma from my phone made the DX3's timer feel a generation behind."
The app and the general ease of use give the Sigma a modern feel the DX3 can't match. Steering the robot from your phone, checking on a cycle from inside, tweaking a schedule in ten seconds, once you've had that, going back to a physical timer feels like a step down.
The feature scores tell the same story. The Proteus DX3 landed a 4, held down by the hidden restocking fee and the lack of advanced filtering even though the timer and coverage are decent. The Sigma earned a perfect 10 for its full feature set, the app, and that three-year warranty. That's a big spread, and it's earned.
"If you want the most capable robot of these two, the Sigma isn't close."
Usability matters just as much day to day. The DX3's controls are simple enough, but without an ergonomic handle or the smarter design touches, it feels a bit clunky to actually use. The Sigma's design and app tie the whole process together and make it genuinely easy to run and keep running.
Put it together and the Sigma's feature set justifies the higher price. The DX3 is solid and reliable, but it lags on the advanced stuff and the little conveniences. If you're paying for ease and real technology, the Sigma is the clear winner here.
Curious how these two stack up against the rest of the field? My best pool robots page has the full shortlist of the top-rated cleaners I've put through the same tests.
Conclusion
Put the Dolphin Proteus DX3 and the Dolphin Sigma next to each other and the contrast is stark. The Proteus DX3 finished with an overall score of 6/10. It's dependable and does the basics well, but the limited coverage and that restocking fee hold it back.
The Sigma landed at 9.8/10, and it earned every bit of that. Dual filters, app connectivity, a three-year warranty, and full waterline coverage add up to a robot that just does more. Its commercial-grade roots are a real part of why it sits at the top of the Dolphin lineup.
Head to head, the Dolphin Sigma is the winner, no hesitation. It cleans more of the pool with less effort from you. If you're ready to spend for a premium cleaner, this is the one I'd tell you to buy.
That said, don't count the Proteus DX3 out if you just want dependable, entry-level cleaning and can live with its rough edges. And if you're weighing other options, the Dolphin Cayman, Dolphin Quantum, and Dolphin Premier are all worth a look for what they each do well.
The right robot really comes down to your pool and how you like to maintain it. The Sigma leads on technology and performance, while the Proteus DX3 covers the reliable basics. For the full picture, my best pool robots page walks through the whole rounded-up selection.
Alternate Robots
If you want alternatives that can match or beat the Proteus DX3 and the Sigma, start with the Dolphin Premier. It's one of the best I've tested for filtration and full pool coverage, waterline included, and it's a natural step up if the Sigma has you interested.
What makes the Dolphin Premier stand out is its Multi-Media filtration: an oversized leaf bag, NanoFilters, and a standard fine filter. Between the three, it catches everything from big leaves to fine sand, so the water stays clear. A dual motor system gives it the muscle to handle even a badly neglected pool.
"The Premier's Multi-Media filters catch everything from leaves to sand."
The Dolphin Premier also brings smart navigation, so it cleans in a methodical pattern instead of bouncing around at random. Add the waterline cleaning, a media-alert system that tells you when the filter's full, and a three-year warranty, and you've got one of the most dependable hands-off cleaners around.
The other one I'd put on your list is the Dolphin Cayman, which is the value standout in the mid-range tier. It runs SmartNav 2.0 for efficient cleaning paths, climbs walls well, and packs the MaxBin, a much larger filter bin that holds more debris so you're emptying it less often.
The Cayman also has a programmable weekly timer, so you can set it and mostly forget it while it keeps the pool maintained on its own. It doesn't do the waterline the way the Premier does, but for the price and the feature set, it's an easy recommendation for a lot of pool owners.
"The Cayman hits the sweet spot between price and real features."
If you want something easy to use that just performs, the Cayman is a strong pick. And if you want the top of the range that does nearly everything well, the Premier is the one to reach for.
Want to compare even more of what I've tested? My best pool robots page has the full lineup so you can find the right fit for your pool.