I liked the handling of the XXX4 slightly better but it does break alot. the other problem I have is that when it rolls the pack comes out the side no matter how tight you pin it. Never had that happen on the SBV2 but did have the axle screws back out a few times while driving. 2 fixes for that - put a drop of locktite between the aluminum cones, or loctite the screw in, both will remedy this problem.
We're trying a Kyosho ZX5 this year too, so far no problems with that one but the shock tower mounts look to be a weak point.
A-Main and Stormer usually have a good supply of V2 parts, or you can order direct from MRC.