I have ran both FI and GTHAUS.
1. Fast Intentions - Magnaflow Mid-Pipe with SS Mufflers
2. Fast Intentions - 18" Resonated X-Pipe with CF MUfflers
3. Fast Intentions - 12" Resonated X-Pipe with SS MUfflers
4. Fast Intentions - 12" Resonated X-Pipe with SS Mufflers and Resonated HFC's
5. GTHAUS Full Catback with stock cats and with HFC's
Sound with stock cats alone and GTHAUS is phenomenal even compared to any previous setup IMHO.
I agree with Vivid Racing, side by side there is no comparison, sound was a huge difference between Meisterschaft and any of my previous FI setups although a non resonated FI setup with RHFC's sounds very good too.
Will one exhaust make more power than the other? Yeah probably but that was not my goal here.
My car has always been daily driven very low (Slammed) so another reason why I got away from FI was because I destroyed 2 sets of mufflers.
Quality is all there and worth every penny you get with GTHAUS. Lowered car friendly was also a huge plus even though
I love the angled mufflers from FI I prefer the way GTHAUS stacked there system so the clearance is great even when I air down 
