GT06GT

its mainly sound. You get slightly more low end torque with the H and slightly more HP with the X at the top end. You can chirp harder with an X, and u can launch harder with an H. Your going to see about a 5 foot pound difference in either torque or HP between both, so dont let the "awsome" H pipe low end torque make the difference. basically H pipe is more old school bad *** muscle car noise, where X pipe is more the ferrari type sound, but definally not the same, just not the motor boat sound