The Triton Boats 1550 SS 2008 is a modified-V design and the Triton Boats A1648 SFB-M 2012 is a flat-bottom 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.
Both boats share a closely matched power ceiling - 25 hp for the Triton Boats 1550 SS 2008 and 35 hp for the Triton Boats A1648 SFB-M 2012. 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 Triton Boats A1648 SFB-M 2012 is rated for 4 passengers, while the Triton Boats 1550 SS 2008 caps at 3. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Triton Boats A1648 SFB-M 2012 could be the deciding factor.
Bottom line: Choose the Triton Boats A1648 SFB-M 2012 if your priority is putting more people on the water - it handles 4 passengers and at 15,8 ft it has the deck room to back that rating up comfortably. The Triton Boats 1550 SS 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 3 that costs less to run day-to-day.