No subjectiveness, H pipe sounds better, that's y they come w one from the factory! Haha.
I can't imagine any H pipe sounds different from another enough to be able tell the difference. The Mac Pro chamber is a little different since it's a chamber (from my understanding) so there is more volume in it than the H piece of pipe. I almost went with the Mac but if I remember correctly, they don't offer a true 3". I have a Borla 3" touring catback which came with an X pipe, switched out the X for a MBRP H pipe. Honestly I could've lived with the Borla X on that system, it's nice, some rasp but so much more mellow than other systems I've heard. The H pipe gives a little more rumble, especially with back pressure when downshifting.
I think the Mac Pro chamber is seriously worth considering though.
'12GT Premium, Roush TVS & BAP, VMP, 82mm pulley,JLT CAI & Catch Can, Eiback Sports, Steeda Cambers & Adj UCA, Adj panhard & Brace, LCAs, Relo Brackets, Diff Bushing, Ford Racing Diff Cover, Axle Catch Can, 3.73, Shaftmasters DS, MGW, BG Syncrp II, Blowfish Shifter Support Bracket & Safety Loop, Trans Mount Insert, MBRP 3" H pipe, Borla 3" Touring Pipes/Axlebacks, BlackCat Gauge Face, Boss Lower Fascia, High Flow GT Grill Insert