H is what I have, with Flowmasters. My cobra kind'a starts to whine in high first and people ask if it's supercharged?.(it was..450 HP w/supercharger but I sold it) I Believe X is a little louder, but ask around it depends on what you want.
Over all i think the two are pretty close to each other. If i remember right the x-pipe gives you a few more horses(like 1-3) than the h, but the h sounds more aggressive (and is a little cheaper to buy). It basically depends on what sound you want/what you like.
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