X & H pipe vs straight dual exhaust

One of the mopar mags years back had a dyno test of Dave Dudeks old challenger were he swapped from a TTI H pipe to a TTI X pipe. He picked up some power but I dont think it was huge. Ive talked to a few guys that said they switched back to H pipes just because they didnt like the tone of the X so Im guessing the difference at the track isnt huge between the two.