I have VST/32 and I upgraded to SX then crossgraded to N2 (while keeping SX license). Now there is SX2.

In my opinion, SX/SX2/N2 are way better than VST. Better sound, better interface, mutliple undo so on and so forth. VST has some midi features that are lacking in SX/N2, SX2 catches up with VST + it adds lot more features more than VST. N2.1 (next release of N2 in October) gets all features of SX2. I use SX with Wavelab4 nowadays.