Help me choose
Our pick: Dolphin Sigma
Dolphin Sigma is the Pool Express pick in this matchup. Dolphin Sigma adds gyroscope-assisted navigation. Dolphin Sigma includes a 55 ft cable with anti-tangle swivel.
M-Line
Dolphin M550
Inground pools up to 50 ft that need floor, wall and waterline cleaning with app control, Pick-Up and a caddy.
ProLine
Dolphin Sigma
Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.
Why Dolphin Sigma is our pick
Dolphin Sigma
Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.
$2,399
Buy Dolphin SigmaDolphin M550 or Dolphin Sigma: our take
Dolphin M550 and Dolphin Sigma are compared on pool fit, cleaning reach, debris handling, controls and ownership details. The recommendation is based on the job the robot must do—not a simple feature count.
Pool fit and cleaning reach
Both robots are intended for inground pools. Both are rated for pools up to 50 ft. Each cleans floor, walls, and waterline, so coverage alone does not separate them. Dolphin M550 lists 2 active brushes and CleverClean navigation. Dolphin Sigma lists 2 active brushes, SmartNav 3.0 with gyroscope navigation, and Triple commercial-grade DC motors.
Filtration and debris
Dolphin M550 includes Basket and UltraFilter; Dolphin Sigma includes Standard filter and NanoFilters. Both have documented fine-debris media, so basket capacity and ease of cleaning matter more than fine-particle capability. Dolphin M550 also has the better documented path for bulky leaves and larger debris.
Controls and day-to-day ownership
Dolphin M550 provides a weekly timer and smartphone control; Dolphin Sigma provides a weekly timer, smartphone control, and included remote control. Dolphin M550 uses continuous corded power, while Dolphin Sigma uses a 55 ft corded cable with an anti-tangle swivel. Dolphin M550 is listed at 22.6 lb versus 24.6 lb for Dolphin Sigma; that 2 lb difference matters when lifting the robot from the pool.
Price, warranty and the decision
Dolphin M550 is listed at $1,999 and Dolphin Sigma at $2,399; Dolphin M550 is $400 less. Each lists a 3-year manufacturer warranty. Pool Express pick: Dolphin Sigma. Dolphin Sigma adds gyroscope-assisted navigation. Dolphin Sigma includes a 55 ft cable with anti-tangle swivel. Choose Dolphin M550 when it is the better fit for shoppers prioritizing the lower $1,999 starting price.
Feature check: what each robot actually has
A green check means the feature is documented as included. A red X means it is documented as absent. A dash means the source does not make the feature clear.
| Feature | Dolphin M550 | Dolphin Sigma |
|---|---|---|
| Cleans the pool floor | Yes | Yes |
| Climbs and cleans walls | Yes | Yes |
| Scrubs the waterline | Yes | Yes |
| Fine-debris filter included | Yes | Yes |
| Large-debris filter | YesEdge | No |
| Automatic scheduling | Yes | Yes |
| Smartphone app | Yes | Yes |
| Anti-tangle swivel | Yes | Yes |
| 3-year warranty | Yes | Yes |
| No recharging between cycles | Yes | Yes |
| Built-in UV-C water treatment | No | No |
Unknown is not treated as “no.” Specifications come from the product pages, current catalog records and manufacturer material collected for this site.
Where Dolphin M550 stands out
Dolphin M550 is the better fit for shoppers prioritizing the lower $1,999 starting price.
- Includes a large-debris bin or bag for leaves
- Is listed $400 lower
- Weighs 22.6 lb versus 24.6 lb
Where Dolphin Sigma stands out
Dolphin Sigma is the better fit for inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.
- Adds gyroscope-assisted navigation
- 55 ft cable with anti-tangle swivel
Dolphin M550 vs Dolphin Sigma specifications
Use pool fit first. Price and app control do not make up for a robot that cannot cover the length or surfaces you need cleaned.
| Specification | Dolphin M550 | Dolphin Sigma |
|---|---|---|
| Best fit | Inground pools up to 50 ft that need floor, wall and waterline cleaning with app control, Pick-Up and a caddy. | Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris. |
| Starting price | $1,999 | $2,399 |
| Pool type | Inground | Inground |
| Maximum pool length | Up to 50 ft | Up to 50 ft |
| Cleaning coverage | Floor, Walls, Waterline | Floor, Walls, Waterline |
| Power | Corded | Corded |
| Filtration | Basket, UltraFilter | Standard filter, NanoFilters |
| Scheduling | Weekly schedule + app | Weekly schedule + app |
| App and remote | App control | App + included remote |
| Cable | Not listed | 55 ft with anti-tangle swivel |
| Robot weight | 22.6 lb | 24.6 lb |
| Warranty | 3 years | 3 years |
Choose Dolphin Sigma
Dolphin Sigma is the Pool Express pick in this matchup. Dolphin Sigma adds gyroscope-assisted navigation. Dolphin Sigma includes a 55 ft cable with anti-tangle swivel.
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