GTP has much more aftermarket available then GXP. If staying stock, I'd get the the GXP, if your gonna play with it get the GTP. Transmissions are weak across the range.
(PS the GTP stops at 06, and the GT is the S/C version 07-08)
if you wanted to keep it stock id also say gxp, if you sock away a buncha dough for a built trans
but if your any more than "a hit every now and then" kinda guy id say youll be happier with the v6 for fuel econ and relatively cheap cost of ownership
Stay away from the GXP. I had one, it was 99% stock for a daily driver and I was always at the dealer getting shit fixed. If it was not so damn unreliable and a rattle trap i would have kept the thing and not traded it for my Accord.