When two boats share the same hull type — in this case both the Avalon Somerset - 20 Foot 2008 and the Avalon Windjammer 18 ft. 2009 are pontoon designs with aluminum 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 Avalon Windjammer 18 ft. 2009 measures 18,0 feet overall (2009), giving it roughly 16,0 additional feet of deck space compared to the Avalon Somerset - 20 Foot 2008 at 2,0 feet (2008). Weight tells a clearer story for trailering families: the Avalon Somerset - 20 Foot 2008 tips the scales at 187 lbs — 171 lbs more than the Avalon Windjammer 18 ft. 2009 at 16 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 100 hp, the Avalon Somerset - 20 Foot 2008 has a 25-hp advantage over the Avalon Windjammer 18 ft. 2009's 75-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Avalon Somerset - 20 Foot 2008 carries 36 gallons versus 24 gallons in the Avalon Windjammer 18 ft. 2009. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Avalon Somerset - 20 Foot 2008 is rated for 12 passengers, while the Avalon Windjammer 18 ft. 2009 caps at 8. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Avalon Somerset - 20 Foot 2008 could be the deciding factor.
At this size, power-to-weight ratio matters more than outright horsepower. The Avalon Windjammer 18 ft. 2009 comes in at 0 lbs per hp versus 2 lbs per hp for the Avalon Somerset - 20 Foot 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.
Bottom line: Choose the Avalon Somerset - 20 Foot 2008 if your priority is putting more people on the water — it handles 12 passengers and at 2,0 ft it has the deck room to back that rating up comfortably. The Avalon Windjammer 18 ft. 2009 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 8 that costs less to run day-to-day.