GG is a high paced game, so when I'm playing it, my hands are fidgeting quite a bit. Not very comfortable when you have to concentrate on the screen inbetween you hands. Also, the buttons feel different compared to a PS2 controller, the lack of grips on a PSP gets in my way of comfortably holding it, you had no shortcuts by default, and the screen was shrunk to widescreen so half the characters obstructed a part of their life bar.
BlazBlue doesn't have to worry about the last complaint, as it's widescreen natively. And you'll still be able to use R as one of the shortcuts. The others still apply.
But that's just me. I'm awkward when playing any game on a portable.
I say if you don't have a PS360 but you do have a PSP, do yourself a favor and pick this up. But if you already have it on a console, there's no reason to buy this new version.