I went with a procharger on my small block only because I already had it lying around from another project I parted out and also because I love the sound of a big overlap cam.

With that said, I don't think I have ever seen anyone who DIDN'T go significantly faster after changing out their procharger for a turbo. Of course most guys who go from superchargers to turbos are also changing other things in the process, but the exhaust restriction of a turbo I'd imagine wouldn't be nearly as much of a parasitic loss as the belt drive of a blower. Not to mention you don't have to worry about belt slip ever.

I think the nicest thing about turbos is being able to dial the boost in very easily to meet track/street conditions.