I've owned both, Boosted with both & have enjoyed both.
I traded my Borla for the N2 about a month ago for the simple fact that I wanted better flow for higher boost level. Borla would have done the job, but i would have wanted to customize it anyway. I actually have noticed a slight decrease in power from the swap to say the least.
Borla: (Overaxle)
Pros: Mid Volume, nice rumble, great wot sound especially with headers, good backpressure for S/C tibs. Great looking tips.
Cons: Cabin drone is loud, no doubt. Supercharging did reduce the drone however :3_yes:
Too Restrictive for Stage 3+/Assassin S/C or Turbo.
N2: (Underaxle)
Pros: Lovely flowing sound, smooth, nice idle, very exotic wot. Good flow for higher boosted tibs.
Cons: Overly loud when you don't want it to be. Fitment (Hangers may need adjustment), Tips are weak sauce.
youtube.com/iwbtib for some of my soundclips of both =)