Hmmm. Keep in mind that the "X" stands for "Cross," and that unlike some companies, Stockli takes its designations seriously. So IME the X's ski somewhat differently than the SC's, which are truly a hybrid SL/GS design. And the non-FIS different yet. They're not all interchangeable.
Differences: The CX and SX are designed as stubby GS skis, with deeper sidecut. But they're fairly stiff, especially in front, and are meant to handle big surface changes at speed. Go watch some comps in Skicross to see what I mean. So they can handle actual courses well (I'd prefer the CX for SL, the SX for GS) but in reality their flex pattern is better for charging variable snow at silly speeds. If Sierra Jim - who's an honest-to-god expert, not an Epic self-rated expert, and not a lightweight either - found the SX could bust his a*ss if he wasn't paying attention, and concluded he'll put it over with his shop's racing skis, perhaps a forewarning to the rest of us who think it'd be perfect for a daily driver. Some people like Porsche Turbos for a daily driver too. I'd go more for the Boxster S.
The SC is designed for groomed frontside surfaces, advanced to expert level, and actual league racing. It has a more supple tip and tail for getting in and out of turns, so it's often called more "playful" in places like bumps than the X's. I agree, and would underscore that playfulness in this context does not mean weakness. It's also nicer in soft snow. But not as much of a master blaster. IME, it's the best daily driver of the bunch, with the CX a close second. Think Boxster S vs. Carrara 4.
The non-FIS models GS and SL are detuned for very high end recreational, and for masters and league racing. But they retain the event-specific handling and feel qualities of their FIS brethren, just easier to manage. My very limited time on one was wonderful. Not relaxing, but wonderful.
I honestly cannot see the point of using the FIS models for anything except racing or training, but that's prolly just me.
Edited by beyond - 5/13/13 at 7:44am