The Bassani axle-back is a great system, other than sticking out too far past the bumper IMO. As far as the X or H pipe debate, generally the H will sound lower in tone (not volume, just tone or pitch). However, I've heard several different X pipes on different vehicles and although they are the same basic design, they can sound radically different even on the same vehicle (assuming that you're talking about a catted design, not off-road).
Case in point, atleast with the with Mach 1 platform (I had an '04 Mach previously), a catted Bassani or SLP X pipe with a Borla catback sounded high-pitched and tinny. But, the same Borla catback with a Magnaflow X sounded noticeably lower, and really good in my opinion. That's the other thing to remember: exhaust sounds are totally subjective. What you may dig, I may hate. Gotta take things with a grain of salt.
ts