I suppose it comes down to a few things really...how much you're prepared to spend, what you're going to do with the machine, whst you want to cut, how often you're going to use it, the accuracy you want from the machine. If you want to make pcb's every other weekend with the odd bit of V carving plaques/signs then V wheels will be fine. If you're wanting to make money from it making aluminium parts then they're the wrong thing....its horses for courses.

If you look at my rambling build you'll see i started out with skate bearings and unsupported pipe and the gantry made from 25mm Sq aluminium box section...what I've ended up with is something way different...but then the things I want to cut have expanded as I've seen what CNC Routers are capable of.....