The Achilles 140SB 2009 is an inflatable design and the Achilles SU-16 2008 is a rigid inflatable design, so you're likely deciding between two noticeably different on-water experiences. Hull type shapes everything from ride quality and fuel burn to dock handling and resale trajectory.
On paper these two are close siblings in the size department - Achilles 140SB 2009 at 14,0 ft versus Achilles SU-16 2008 at 16,0 ft. Weight tells a clearer story for trailering families: the Achilles SU-16 2008 tips the scales at 378 lbs - 223 lbs less than the Achilles 140SB 2009 at 155 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 Achilles SU-16 2008 tops out at 75 hp. Engine specs for the Achilles 140SB 2009 aren't listed - confirm with a dealer before selecting an outboard.
For family outings this is probably the sharpest distinction between the two. The Achilles SU-16 2008 is rated for 9 passengers, while the Achilles 140SB 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 2008 could be the deciding factor.
Bottom line: Choose the Achilles SU-16 2008 if your priority is putting more people on the water - it handles 9 passengers and at 16,0 ft it has the deck room to back that rating up comfortably. The Achilles 140SB 2009 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 4 that costs less to run day-to-day.