Both the Malibu 21 vRide (2009) 2008 and the Malibu Response LX 2012 are modified-V designs, both built in fibreglass, 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 - Malibu 21 vRide (2009) 2008 at 21,0 ft versus Malibu Response LX 2012 at 20,0 ft. Weight tells a clearer story for trailering families: the Malibu 21 vRide (2009) 2008 tips the scales at 3 500 lbs - 1 050 lbs more than the Malibu Response LX 2012 at 2 450 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.
For family outings this is probably the sharpest distinction between the two. The Malibu 21 vRide (2009) 2008 is rated for 11 passengers, while the Malibu Response LX 2012 caps at 8. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Malibu 21 vRide (2009) 2008 could be the deciding factor.
Bottom line: Choose the Malibu 21 vRide (2009) 2008 if your priority is putting more people on the water - it handles 11 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Malibu Response LX 2012 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 8 that costs less to run day-to-day.