Get the Hyper 8.5 if you are planning on getting the Hyper. The 8.5 has a slew of improvements that make it much easier to drive, and it performs better!

The Xray is a fantastic product that won't give you any worries about durability. That being said, Xrays have been known to take a significant amount of testing and tuning to get a proper setup for any given track.

They Hyper 8.5 is probably a little easier to setup and definitely handles better based upon what I've seen personally.

I wheel a 8.5 with the Jammin' Super Bore Shocks (16mm) and regularly eat Xrays for breakfast at the club/sportsman levels of competition.