I assume you mean the cat back system vs the axle back…? Axle back is just mufflers, the cat back includes the resonator replacement. It’s a giant heavy “suitcase” after the cats, that you can replace with straight pipes, H pipe or X pipe.
I have the Ford Performance by Borla system, which is very close to the Atak. I have the cat back system and am very happy with it. Removes a lot of weight and provides a great sound.
I second above. The axle back (just mufflers) leaves the huge factory resonator unless you opt to replace it separately . If you have a completely stock system I think the whole cat back is the best way to go that way you replace the resonator and have a fully engineered system all the way back. That's the way I went and love it. Took off my factory exhaust all in 1 piece . It's HUGE.
Exhaust system #6 was a butchered GT cat back with an H - pipe and Borla S Type mufflers. Sounded great but was a bit loud for me for freeway cruising. However I had zero drone (finally)! I ended up removing the H pipe and reinstalling the GT resonator (which I think is the same as the v6 version)…perfect for me. Sounds great when you jump on it, but quite livable on the freeway - only slightly louder than OEM. It’s much louder under heavy throttle. And I could feel a noticeable difference in performance with the Borla mufflers over the stock GT mufflers.