My opinion is that it depends on what you can afford, what you want it to look like, how long you want it to look that way, and what kind of performance is being routed through them, and what you can afford. Did I mention the what you can afford part?
Like , you wanna go fast? How much money you got?
I don't know enough about the fancy x and H pipe systems to offer an opinion on them, I know those depend on which RPM range you need to work in. Long tube though, the more bends in a system the more back pressure (to a point). Ever wonder why super high horsepower engines run pipes straight out the exhaust? (ETA- I meant the exhaust PORTS) So no bends have to be in the system.
And one more opinion of mine, in front of the rear wheels, I love exhaust that exits in front of the rear wheels on both sides. I (think it) looks cooler from the back on a cool morning.