I believe the V3s use a slightly smaller diff unit making the whole thing lighter/ smaller overall, along with different bearings or something- the input shaft will accept a 5mm bore cup I believe, compared to the older style one which uses an 8mm bore cup? Also seems cheaper unless Im mistaken.
The V2s should be fine though, just make sure you assemble them correctly and shim them carefully to remove excess play, then they'll last a very long time.
