As Steve mentioned, the 21 LSV rides on the Diamond hull which is designed to create more lift so the boat rides higher in the water. The result is that it handles a bit better than the VLX, has a better slalom wake, and rides a bit rougher. If you're a family that does everything and wants a boat for boarding, skiing, tubing and cruising, the 21 LSV is a good choice. If you spend more time skiing than wakeboarding, the 21 LSV is
the choice.
Check out
MBO for more information on the 21 LSV. There are 4 or 5 members that have LSV's decked out to similar specs as the VLX, and I'm sure they can give you some feedback.