We have tested both the Dolphin Cayman and the Dolphin Sigma in real pools, measured their suction at the intake, and lived with the filtration and daily routine each one requires. This comparison brings those results together so you can see the real-world trade-offs without relying on the numbers printed on either box.
Dolphin Cayman and Dolphin Sigma are close enough in the same lineup that the feature and value differences matter as much as the badge.
The short answer: Dolphin Sigma is our pick. Its 2.0 PSI reading, wide intake, NanoFilters, and underwater app make it the most complete connected Dolphin. Dolphin Cayman still has a clear case: it is the better fit for smaller pools that need set-and-forget cleaning on a sensible budget.
Quick Answer
Buy the Dolphin Sigma when its strengths match your pool. Best for: buyers who want near-Premier power with full app control. It is the stronger choice across the measurements and ownership factors that matter in our testing.
Choose the Dolphin Cayman instead when its narrower advantages matter more to you. Best for: smaller pools that need set-and-forget cleaning on a sensible budget. It delivers dependable 1.5 PSI corded cleaning, a weekly timer, and an easy top-load basket.
Our calls in the full reviews are Recommended for the Dolphin Cayman and Recommended for the Dolphin Sigma. Those calls matter here: PSI is the first round, not the entire verdict.
Suction Power: 1.5 PSI vs 2 PSI
On our hydro manometer, the Dolphin Cayman measured 1.5 PSI and the Dolphin Sigma measured 2 PSI. That gives the Dolphin Sigma a 0.5 PSI advantage, or about 33% more intake pressure than the lower reading.
We measure pressure directly at the intake with the same gauge and pool setup. That is different from manufacturer flow-rate claims in gallons per hour: GPH describes water movement, while PSI shows how hard the intake pulls on debris. Cordless results are recorded at full charge. Our complete pool-robot suction test explains the method and shows where both robots sit on the full board.
The number needs context. It delivers dependable 1.5 PSI corded cleaning, a weekly timer, and an easy top-load basket. Its 2.0 PSI reading, wide intake, NanoFilters, and underwater app make it the most complete connected Dolphin. The stronger gauge result gets this round, though intake pressure alone cannot make up for a filter that lets fine debris escape or a routine that makes you handle the robot every day.
Filtration and Debris Handling
The Dolphin Cayman uses top-loading maxbin with optional nanofilter panels. The Dolphin Sigma uses top-loading pleated nanofilter cartridges for fine dust, pollen, and silt.
We give the filtration edge to the Dolphin Sigma. Our comparison favors fine-particle capture, usable debris capacity, easy cleaning, and whether the better filter is included rather than sold as an upgrade.
For leaves, capacity and intake design matter. For pollen, silt, and the haze that dulls otherwise clear water, the filter media matters more. A basic mesh screen can look clean after a run while still passing the smallest material back into the pool.
Automation and Daily Work
The Dolphin Cayman is corded. Weekly timer on the power supply; no app or charging. The Dolphin Sigma is corded. MyDolphin Plus app works underwater and supports weekly scheduling.
Because both are corded, neither needs a recharge. The meaningful question is how much scheduling and remote control each power supply or app provides.
We score automation as a tie.
Coverage and Pool Fit
For the Dolphin Cayman, our review found floor and walls in smaller pools, with a compact 50-foot cable. The Dolphin Sigma is built for floor, walls, and waterline with the widest intake path we have measured.
The Dolphin Sigma wins the coverage round on the breadth of surfaces and pool situations it can handle.
This is where the runner-up can still be the smarter fit for specific pools. A compact pool does not benefit from paying for reach it cannot use, while a pool with a sun shelf, long waterline, or heavy leaf load can expose the limits of a simpler machine quickly.
Value: Performance for the Money and Time
Our value take on the Dolphin Cayman: One of the strongest price-to-performance buys in the tested group. For the Dolphin Sigma: Expensive, but it combines elite suction, filtration, navigation, and app control.
The value edge goes to the Dolphin Cayman.
Value is not the same thing as the lowest checkout price. We count cleaning power, filtration, how many surfaces the robot covers, and how often you have to retrieve or charge it. A cheaper robot that leaves you vacuuming behind it is not a bargain, and an expensive robot only earns its price when its extra capability solves a real problem in your pool.
Which One Should You Buy?
- Buy the Dolphin Sigma when its strengths fit your pool. Best for: buyers who want near-Premier power with full app control. Its 2.0 PSI reading, wide intake, NanoFilters, and underwater app make it the most complete connected Dolphin.
- Choose the Dolphin Cayman instead when its specific trade-off fits better. Best for: smaller pools that need set-and-forget cleaning on a sensible budget. It delivers dependable 1.5 PSI corded cleaning, a weekly timer, and an easy top-load basket.
- Know the main drawback: Dolphin Sigma — Its premium price is hard to justify if a power-supply timer is all the control you need. Dolphin Cayman — It skips app control, an anti-tangle swivel, included NanoFilters, and dedicated shelf cleaning.
Final Verdict
Dolphin Sigma wins this comparison. Dolphin Sigma wins the overall matchup. Its 2.0 PSI reading, wide intake, NanoFilters, and underwater app make it the most complete connected Dolphin. Dolphin Cayman remains the better fit for smaller pools that need set-and-forget cleaning on a sensible budget.
Read the complete Dolphin Cayman review and Dolphin Sigma review for every test photo, setup detail, and long-form ownership note. You can also return to all pool-robot comparisons to see any other matchup from the 19 cleaners in our test set.
