When two boats share the same hull type — in this case both the Achilles SPD-310 2009 and the Achilles SU-16 2009 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 SU-16 2009 measures 16,0 feet overall (2009), giving it roughly 5,8 additional feet of deck space compared to the Achilles SPD-310 2009 at 10,2 feet (2009). Weight tells a clearer story for trailering families: the Achilles SU-16 2009 tips the scales at 378 lbs — 277 lbs less than the Achilles SPD-310 2009 at 101 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 75 hp, the Achilles SU-16 2009 has a 65-hp advantage over the Achilles SPD-310 2009's 10-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 SU-16 2009 is rated for 9 passengers, while the Achilles SPD-310 2009 caps at 4. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Achilles SU-16 2009 could be the deciding factor.

At this size, power-to-weight ratio matters more than outright horsepower. The Achilles SU-16 2009 comes in at 5 lbs per hp versus 10 lbs per hp for the Achilles SPD-310 2009. 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.