Cubase definately I reckon.
Apple's own DAWs (Garageband and the Logics) don't support VSTs.
Though an increasing number of plug-ins supplied as VSTs are increasingly also supplied as AUs (Apple's plug-in format). That's not much help with one's legacy VST stuff, of course -- but switching platforms is like that!
I tried Cubase, but didn't really get on with it. I really like GarageBand's interface, and it's limitations haven't annoyed me enough yet that I've felt like springing for Logic SE. On the other hand, I've heard that Logic's interface is not as pleasant as GarageBand's ....
Garageband is definately the friendliest, its what I mostly use. I also have Cubase LE and *cough* Logic Express *cough* (can't remember where I got it :roll: ) and they are definately more professional (writing midi is much easier for example) but don't have the plug'n'play of Garageband that I love, its almost like a taperecorder in comparison you can get ideas down so fast.
That said I do have two plug ins that only seem to work in Cubase, BBE Sonic Maximizer is VST only and the SSL LMC compressor (instant 80s drum sound) isn't recognised by the apple software even though I have the AU but the VST is picked up by Cubase.
PS, Addictive Drums from XLN Audio is awesome, it's what I plan on getting instead of EZdrummer as soon as funds allow (I also need the full version of izotope ozone)