I just purchased the Injen exhaust (raw unfinished tip) for my 2015 (Cobb FMIC, RMM, Intake, and Pro Tune by Randy). It was a competition between Cobb and Injen, and Injen won partly because of price ($599 shipped from Modbargains via their Labor Day Sale) and also because of how the Injen exhaust sounded on video at higher rpm. Hopefully I like it as much in person.
I really like the sound of the Cobb system too, and I hope that I don't regret my choice. Both exhaust look well made, and I don't have much of a preference between the single and dual tip. I bought the Cobb hangers with the exhaust, and to me as long as the system performs and isn't too intrusive in the cabin while relaxed cruising then I will be very happy.
I datalogged yesterday and uploaded to a Virtual Dyno Graph, and my car according to VD is putting down 190 whp (93 octane) and 271 lbs trq. I have a saved car profile (smoothing 3) and will datalog again with the same variables to see if the Cobb AP and VD register any gain after install and once the ecu adjust to the new CBE. I don't plan to go to an aftermarket DP (at least anytime soon), and so my current pro tune should also do fine with just a CBE. Ultimately with my current setup plus the new CBE, I would be very happy to VD at 200 whp max and stay at or a little above my current max trq.