Quick answer, claudiu... Acid is better if you want to work with sampled loops a LOT, Cubase is better if you want to work with MIDI a LOT.

Both will do both, but there is a bias...

Me.. I'd go with Cubase 4 (or SX3). I've been using it since the Atari days, and IMO, it's still the best app for MIDI, which you will be doing a LOT of if you use your VA76 as more than just a trigger for the loops...

Oh, and get StylusRMX if you get Cubase (or even AcidPro). Better loops are hard to find...