Difference between the two (X Vs H) is fairly negligible IMHO, just go with what your ears prefer (soundwise - the exotic "X" or the classic "H"). Since you already have straight through mufflers (Magnaflows), many folks would probably just stick with the X-pipe in order to keep that "exotic" sound. Your call though.
i had a off road h pipe on my old 95 gt before i totaled it and it sounded real mean, but im honestaly not sure if i have herd an x pipe how much different do they sound?