From Steinberg's Site:
http://www.steinberg.net/products/in...p;sid=03937424
Cubase VST Mac
Cubase VST combines high resolution MIDI recording with audio recording in either 16 or 24 bit formats
Cubase VST Score Mac
Cubase VST Score combines high resolution MIDI recording and professional score layout and printing, with audio recording in either 16 or 24 bit formats
Cubase VST/32 Mac
Cubase VST/32 combines high resolution MIDI recording with audio recording in either 16 / 24 or 32 bit overload free formats, including `analog sound´ TrueTape™ recording
So with score you get, well, professional scoring (regular cubase has SOME scoring capability), and with 32 you get to mix down to and import 32 bit files (almost infinite headroom), and you get analog tape emulation on recording. It also comes with a better quality reverb. If you don't think you need these professional features, then you should probably get the regular VST, which does most of what the more expensive versions do.