Both the Malibu Response FXi 2011 and the Malibu Response LXi 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?
On paper these two are close siblings in the size department - Malibu Response FXi 2011 at 20,0 ft versus Malibu Response LXi 2005 at 20,0 ft. Weight tells a clearer story for trailering families: the Malibu Response FXi 2011 tips the scales at 3 200 lbs - 400 lbs more than the Malibu Response LXi 2005 at 2 800 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.
Both boats share a closely matched power ceiling - 410 hp for the Malibu Response FXi 2011 and 400 hp for the Malibu Response LXi 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. Both carry nearly identical fuel loads - 40 gal and 41 gal - so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Malibu Response FXi 2011 is rated for 10 passengers, while the Malibu Response LXi 2005 caps at 8. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Malibu Response FXi 2011 could be the deciding factor.
Bottom line: Choose the Malibu Response FXi 2011 if your priority is putting more people on the water - it handles 10 passengers and at 20,0 ft it has the deck room to back that rating up comfortably. The Malibu Response LXi 2005 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 8 that costs less to run day-to-day.