Matching a inflatable non rigid Achilles LS4-RU 2011 against a inflatable rigid Achilles SU-18 2008 means you're likely deciding between two genuinely different on-water experiences. Hull type shapes everything from ride quality and fuel burn to dock handling and resale trajectory.

Size is the most obvious dividing line here. The Achilles SU-18 2008 measures 18,0 feet overall (2008), giving it roughly 9,3 additional feet of deck space compared to the Achilles LS4-RU 2011 at 8,7 feet (2011). At 63 lbs and 44 lbs respectively, both sit in a similar weight class — either should pair comfortably with most mid-size SUVs and half-ton trucks, though always confirm your specific tow rating with the motor added.

The power gap is worth calling out. Rated to 90 hp, the Achilles SU-18 2008 has a 84-hp advantage over the Achilles LS4-RU 2011's 6-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-18 2008 is rated for 11 passengers, while the Achilles LS4-RU 2011 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-18 2008 could be the deciding factor.

At this size, power-to-weight ratio matters more than outright horsepower. The Achilles SU-18 2008 comes in at 1 lbs per hp versus 11 lbs per hp for the Achilles LS4-RU 2011. 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 LS4-RU 2011 is an inflatable design — lighter, easier to store, and quicker to launch from a beach or dock without a slipway. The Achilles SU-18 2008 is a rigid hull, which typically offers a more confident ride in chop and easier maintenance over the long term.