turbo because it'll make 20psi without needing a service every 100 miles and has more progressive power delivery so wont keep (well, hopefully!) blowing up gearboxes. I'm not convinced a g-lader running a small pulley is ideal for track days unless I want to keep spending a lot of money on servicing and replacement parts. K03 turbos can easily be found for £50.
I do miss the noise of the g-lader and the punch-in-the-face power delivery though (which is what kills boxes for fun really).