It matters a lot. What sounds bad on a 05-10 sounds good on a 04 and what sounds good on a 05-10 also tends to sound good on a 04. For example, o/rX and flows sound bad on a 05-10 but sounds good on a 04.
an x pipe is more efficient and will make more a few more ponies than an h pipe but I prefer the sound of an h pipe to an x pipe. IMO thats all exhaust is, its just personal preference, mufflers arent gonna make a ton of power and the power difference between an x and h pipe is negligible
on the 2V engines I still love the H-pipe and super 40s - and I wouldn't give a fawk if everyone else has them! I would kill to have my 3V sound like that