RE: O.S or Novarossi?
Regards the new VZB. You know something must be up when the OS factory guys are still running their old V01's when they can get the VZB for free. Of course when the V01 first hit there were issues with it as well and OS resolved them in due course. Give it some time before you buy.
The P5 is a decent engine for buggy as long as you get a plain purple head Novarossi P5 and not a TOP or REX P5.
Picco 5 ports are known to be weak off the bottom as well as hard to dial in and keep tuned. If you love tweaking on your engine all day and have a really big track that favors top end, it's not bad.
My current fave in 5 port buggy engines are (1) Bergonzoni XR and (2) Crono RS5. The Berg engine is in a word, awesome, but can be hard to come by. The Crono is right up there with the berg in terms of power and reliability. I've compared them side by side and the Berg has an ever so slight edge in the top end department, but other than that they are about the same. The good news on these engines is they cost about the same as a P5.