Both the Avalon Catalina 20 ft. 2010 and the Avalon Somerset 20 ft. 2009 are pontoon designs, both built in aluminium, so 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 - Avalon Catalina 20 ft. 2010 at 20,0 ft versus Avalon Somerset 20 ft. 2009 at 20,0 ft. At 1 750 lbs and 1 800 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 115 hp, the Avalon Somerset 20 ft. 2009 has a 25-hp advantage over the Avalon Catalina 20 ft. 2010's 90-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 Avalon Somerset 20 ft. 2009 is rated for 10 passengers, while the Avalon Catalina 20 ft. 2010 caps at 9. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Avalon Somerset 20 ft. 2009 could be the deciding factor.
Both are 2-tube and 2-tube pontoon designs respectively. Tube diameter and gauge affect stability and load capacity - more so than most buyers realize when comparing on paper.
Bottom line: Choose the Avalon Somerset 20 ft. 2009 if your priority is putting more people on the water - it handles 10 passengers and at 20,0 ft it has the deck room to back that rating up comfortably. The Avalon Catalina 20 ft. 2010 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 9 that costs less to run day-to-day.