Well, it depends on your future plans. If you're going to eventually go with a turbo upgrade, are you set on the ATP, or would you still consider CP-E? If no turbo upgrade is in your future, I beleive the CP-E dp is better for the stock turbo because:
A) It has a more defined bellmouth.
B) It has a smoother transition from bellmouth to pipe.
C) It is available with a cat.
D) If you get the catless, but then change your mind, you can put a cat in without needing an O2 extension.
E) Thanks to yours truely, CP-E might be able to completely eliminate the CEL from the catless version.
On the other hand, if you plan on playing around with different turbos, the V-band is nice. I had one one my evo and it worked with all four turbo swaps I did. I had to do a little welding when I went to a divorced wastegate, but the downpipe worked none-the-less. It all depends on your intentions. Back to back, I doubt there would be any noticable SOTP differences between the two.