Neither will give better power, which one sounds better is entirely up to you. A typical configuration pairs H-pipe with chambered mufflers and X-pipe with straight-through mufflers. But not always. You should find someone locally that has the setup you're thinking about, so you can listen and see what you think.
i have bbk lts, h pipe, and magnaflows and i like the way its sounds. Its way different than my 40 series i had and it doesn't sound like anyone else car around here so im happy