I just spent a bunch of laps on the 18-19 SX Turtle Shell and AX Turtle Shell "Comfort" here in Vermont on some superb carving surfaces and mixed-fresh snow surfaces. In my book, the hot-rod SX is one of the reference standard race-carvers on the planet. Just a superbly balanced blend of auto-engagement, turn shape, power handling, dampness, energy and feedback to make any technical skier become hopelessly addicted. Simply put, the SX is stunning carving instrument of the highest quality when you don't want to drive an SL-only race ski all day. This is a ripping frontside trench-digger with impeccable manners and limitless power handling. When you want to remember what a best-of-breed carving ski feels like, put the SX underfoot. While I love the Head i-series of carvers, I think the Stockl series is just a notch above.
The AX model with "Turtle Shell Comfort" feature has just a wee-hint of tip rocker and different geometry to deliver a ride nearly as intensely satisfying as the SX, but in a more forgiving and adaptable chassis. The AX trades off a bit of carving intensity and surgical accuracy for a slightly looser and forgiving turn engagement up front and an ever-so-slightly less-intensive mid-turn edge-set feeling. The AX does not demand the same level of attention the SX does when you exit your turn under pressure, letting you get a little more relaxed after your apex (if you want). Overall, the AX is more forgiving if you find some fresh snow or cut-up snow on your groomers, but you still wouldn't call the AX an "all-mountain" ski. I think both the SX and AX are groomer-only power carving tools of the highest order, with the purists and SL addicts being suited to the SX, and those with more varied turn radius habits leaning toward the AX.
Both are stunning examples of the same carving prowess in different intensities and levels of forgiveness. The designers at Stockli know this breed of ski perfectly and delivered two models with just enough difference to suit the picky technical carving geeks who crave race-ski performance of the highest quality without the restrictions pure race skis exhibit. I loved these two skis. Great performance and stunning material and construction quality. Premium skis at a premium price.