Both the Malibu 21 vRide (2009) 2008 and the Malibu 23 vRIDE 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 23 vRIDE 2012 at 23,0 ft. Weight tells a clearer story for trailering families: the Malibu 23 vRIDE 2012 tips the scales at 3 900 lbs - 400 lbs less than the Malibu 21 vRide (2009) 2008 at 3 500 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 23 vRIDE 2012 is rated for 15 passengers, while the Malibu 21 vRide (2009) 2008 caps at 11. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Malibu 23 vRIDE 2012 could be the deciding factor.
Bottom line: Choose the Malibu 23 vRIDE 2012 if your priority is putting more people on the water - it handles 15 passengers and at 23,0 ft it has the deck room to back that rating up comfortably. The Malibu 21 vRide (2009) 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 11 that costs less to run day-to-day.