All depends if you think you're going to want to mod it later. There aren't many mods for the GXP, and with the large aftermarket for the 3800, you can mod a CompG to be faster and quicker than the GXP.
I decided on the GXP because I like the front fascia on the GXP much more than the one on the other trim levels, and because I prefer the growl and rumble of a V8 over the whine of a supercharger (even though supercharger whine does kick ass).
Look at it this way; you either end up with a screaming banshee or a roaring beast. Either way, you can't go wrong.
Just listen to your heart AND your wallet.
