When two boats share the same hull type — in this case both the Achilles LSI-335 2009 and the Achilles SPD-365 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?
On paper these two are close siblings in the size department — Achilles LSI-335 2009 at 11,0 ft versus Achilles SPD-365 2009 at 12,2 ft. At 91 lbs and 142 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.
Both boats share a closely matched power ceiling — 15 hp for the Achilles LSI-335 2009 and 25 hp for the Achilles SPD-365 2009. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup.
For family outings this is probably the sharpest distinction between the two. The Achilles SPD-365 2009 is rated for 6 passengers, while the Achilles LSI-335 2009 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Achilles SPD-365 2009 could be the deciding factor.
At this size, power-to-weight ratio matters more than outright horsepower. The Achilles SPD-365 2009 comes in at 6 lbs per hp versus 6 lbs per hp for the Achilles LSI-335 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.
Bottom line: Choose the Achilles SPD-365 2009 if your priority is putting more people on the water — it handles 6 passengers and at 12,2 ft it has the deck room to back that rating up comfortably. The Achilles LSI-335 2009 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.