I have an 08 525XC and my buddy Driver has a 09505 SX, we just got off the dyno with his bike, and mine has lots of dyno runs on it, I like the SX, here we can get an 08XC 525 for $7600, and the SX is $10600.00 the SX is better set up for MX, but 3k more in dollars is alot, both make close to the same power my XC stock w/free mods made 49.5hp and 39.1 ft lbs, the SX made a tad more hp and a tad less ft lbs, the power curve is better on the SX also your choice, I know i'm no help