The Spectre 320 Roadster CC 2012 is a deep-V design and the Spectre 428sc 2010 is a catamaran 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.
For family outings this is probably the sharpest distinction between the two. The Spectre 320 Roadster CC 2012 is rated for 11 passengers, while the Spectre 428sc 2010 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Spectre 320 Roadster CC 2012 could be the deciding factor.
Bottom line: Choose the Spectre 320 Roadster CC 2012 if your priority is putting more people on the water - it handles 11 passengers and at 31,7 ft it has the deck room to back that rating up comfortably. The Spectre 428sc 2010 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.