The SRX is a take no prisinors racer. Its a triple-triple (triple cylinder, triple exhaust pipes) so its very fast on the top-end. Even stock these sleds will do 120 mph. They have a different hood than the SXr, the hood is a lot more bulgy to make room for the pipes.
The SRX has a lot less suspension travel than the SXr. I believe the SRX only has about 6", the SXr has something like 8"-10". However, the SRX does corner a lot better due to its lower center of gravity.
The SXr is much more of a trail sled. Its only got 1 exhaust pipe, so it doesnt make the kind of power that an SRX does. I would estimate the SXr puts out around 115 hp, whereas the SRX is closer to 140. As I said, the SXr has a lot better suspension than the SRX.
The easiest way to remember the difference is like this, the SRX is a lake sled, the SXr is a woods sled.
Hebi