Both the Malibu 21 LSV 2009 and the Malibu iRide 2005 are modified-V designs, 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?
Both boats share a closely matched power ceiling - 400 hp for the Malibu 21 LSV 2009 and 400 hp for the Malibu iRide 2005. 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. Fuel capacity breaks the other way: the Malibu 21 LSV 2009 carries 46 gallons versus 41 gallons in the Malibu iRide 2005. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Malibu 21 LSV 2009 is rated for 12 passengers, while the Malibu iRide 2005 caps at 10. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Malibu 21 LSV 2009 could be the deciding factor.
Bottom line: Choose the Malibu 21 LSV 2009 if your priority is putting more people on the water - it handles 12 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Malibu iRide 2005 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 10 that costs less to run day-to-day.