some exhausts are angled to minimize the pipe bends to the muffler for maximum flow. RSR GT2 for example comes straight out from the exhaust manifold and bends once to point out torwards the opening of the rear bumper.

the cheaper exhaust systems that retain all factory bends while still coming out of the rear angled are all for appearance and cosmetics.

as for magazine results...i dont believe any of them. they are paid to do articles on the products, and most of their setups are not typical anyway.