do you have a cat-back or axle-back exhaust already?
if you have a cat-back, go with the short system.
if you have an axle back, go with the standard system which includes the x-pipe.
if you still have stock exhaust i would go with the short system, then get a cat-back whenever you can afford it! IMO headers with a cat-back is a simpler and cleaner system; no cutting of the stock system required!
the ARH x-pipe is no better than any aftermarket cat-back system, so no need to waste a few hundred bucks on the system with the x-pipe