Bit late, but owning both a C5C and a V01B, I can say that everything FRB has said about the V01B is quite true - i'm yet to see another engine that matches the smooth powerband that it has to offer.
RobH - I can't honestly say there is a glaringly obvious difference in wear time between the RB and OS motors, it's just that the OS likes to be kept rich, and not overheated. If they are both run above what they should be run at, the RB will hold up better. But as long as the OS isn't leaned out more than it should be, it can last just as long. Don't know what it's like over there, but OS replacement parts here are 1/4-1/3 the RB prices, so it's cheaper in the long run to OS it anyway. If they didn't have that advantage though, i'd probably stick to nova/rb.
Sadly, OS has decided to make the replacement pistons for the V01 the same billet/machined ones as the VZB, instead of the original cast ones they came with - and the machined piston is the reason why VZB owners are putting out comments about short lifespans. Some will still stick with OS through this, others will drop out.
Any V01B going on ebay etc will have the cast piston, and you can get many squeezes out of those (osrocket) before you need to worry about getting a new one, so if it was me, i'd still go for it. IMHO, for a smooth racemotor, nothing matches the OS.
The C5 is a rocket, but the powerband is quite on off, would give it a go on the track for fun, but wouldn't be planning on churning hot laptimes with it, at least not on any regular sized track.
And the WS72, well that will fit somewhere in between.
uDi