When two boats share the same hull type — in this case both the Achilles SG-156 Commercial 2011 and the Achilles SPD-335 2008 are inflatable non rigid designs with inflatable construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
Size is the most obvious dividing line here. The Achilles SG-156 Commercial 2011 measures 15,5 feet overall (2011), giving it roughly 4,5 additional feet of deck space compared to the Achilles SPD-335 2008 at 11,0 feet (2008). Weight tells a clearer story for trailering families: the Achilles SG-156 Commercial 2011 tips the scales at 272 lbs — 149 lbs more than the Achilles SPD-335 2008 at 123 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
The power gap is worth calling out. Rated to 55 hp, the Achilles SG-156 Commercial 2011 has a 35-hp advantage over the Achilles SPD-335 2008's 20-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load.
For family outings this is probably the sharpest distinction between the two. The Achilles SG-156 Commercial 2011 is rated for 8 passengers, while the Achilles SPD-335 2008 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Achilles SG-156 Commercial 2011 could be the deciding factor.
At this size, power-to-weight ratio matters more than outright horsepower. The Achilles SG-156 Commercial 2011 comes in at 5 lbs per hp versus 6 lbs per hp for the Achilles SPD-335 2008. The lower the ratio the more explosive the acceleration — meaningful on a short RIB where bursts of speed, quick planing, and agility in surf or tight waterways define the experience.
The Achilles SG-156 Commercial 2011 is an inflatable design — lighter, easier to store, and quicker to launch from a beach or dock without a slipway. The Achilles SPD-335 2008 is a rigid hull, which typically offers a more confident ride in chop and easier maintenance over the long term.
Bottom line: Choose the Achilles SG-156 Commercial 2011 if your priority is putting more people on the water — it handles 8 passengers and at 15,5 ft it has the deck room to back that rating up comfortably. The Achilles SPD-335 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.