The Starcraft Marine 2009 OB 2010 is a modified-V design and the Starcraft Marine STX 206 Viper 2013 is a deep-V 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 - Starcraft Marine 2009 OB 2010 at 20,3 ft versus Starcraft Marine STX 206 Viper 2013 at 20,5 ft. At 2 405 lbs and 2 400 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 300 hp, the Starcraft Marine STX 206 Viper 2013 has a 75-hp advantage over the Starcraft Marine 2009 OB 2010's 225-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads - 51 gal and 50 gal - so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Starcraft Marine 2009 OB 2010 is rated for 12 passengers, while the Starcraft Marine STX 206 Viper 2013 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Starcraft Marine 2009 OB 2010 could be the deciding factor.
Bottom line: Choose the Starcraft Marine 2009 OB 2010 if your priority is putting more people on the water - it handles 12 passengers and at 20,3 ft it has the deck room to back that rating up comfortably. The Starcraft Marine STX 206 Viper 2013 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.