I have the Borla Catback, love it. Not sure if it's any better or worse than any other track exhaust. The Joe-Z has some proven tested numbers by members here. I refuse to put my car on a Dyno, sorry.
It was a pain in the ass to install, I had to go back to the shop twice and it had to be spot welded to the thingamajigger because it would get hot and start rattling. I could not tell you if this is due to a poor installer or poor quality control, but it sounds MUCH better than the stock exhaust. MUCH louder. Coupled with the K&N intake I would turn heads at 3000rpm, higher than that and it roars like no other.
My Borlas fit like a dirty shirt, no installatoion difficulties whatsoever. Overall I'm happy with it. Only beef I have is the drone it makes while cruising at 1800rpm. Most quiet is to cruise at about 3000rpm at just about 200kph.
Something you might want to consider is adding sound deadening like Dyna-Mat under the carpet in the trunk. I just ordered the Borla and was hoping it wasn't going to drone but heck, does it sound bad a$$ under WOT? LOL
The exhaust fills the gap where the intake cannot. WOT is dominated by k&n intake roar. Low rev is where the exhaust comes in. If you live in a cold climate, cold starts are excessively loud with the Borla.
I keep sport mode on, the drone can be irritating at times.