Originally Posted by Jim S
I have no clue.
I started a similar thread during the X-games. I had previously heard that guys were using GS race skis with "sx:11" or "crossmax" top sheets. I also noticed that lots of racers were using standard GS skis like the Fischer RC4. Anyway, people here confirmed that for actual skiercross racing guys are using GS race skis with "cross" top sheets. This is because Skiercross really doesn't lend itself to a "turny" 16m or 17m radius ski, but it is great marketing for the ski companies to make it appear that "cross" skis are being used.
That being said, the above post is correct. In terms of retail "cross" skis the radius is <21, unlike FIS approved race skis. Also, they are offered in shorter lengths. As I understand it those are the main differences. A "cross" ski will be better for most people who want to have fun and carve around, as compared to a GS race ski with a 21+ FIS approved radius that will require more work to turn.