No other exhaust system I've heard sounds as good as the Borla ATAK. It has the same kind of 60's muscle car sound that the Carven & Flowmaster Outlaw has, but a smoother and more refined quality about it.
The ATAK also has this sweet kind of gurgle at idle that somewhat reminds me of the Fox Body Mustangs with Flowmaster 40-series. It also doesn't drone in MDS (4-cylinder mode) like the muffler only systems. It's tuned to sound well even when in 4-banger mode.
In the end, all these muffler options sound great for the price, but if you want the best sound in the "louder" category, it's the Borla ATAK.