Dawgcatching did a direct comparison last year. He thinks very highly of both. Search.
I own the FX94, did own the old Stormrider, have not skied the new one. All I can say is that I'd bet the FX94 is a bit more forgiving and finesse oriented ski. Hard to compare tips, since the Kastle cut outs tend to be light and give lots of feedback, but are not particularly soft or easy to deviate. While apparently the new SR's apparently are .3 mm metal at the tip and tail, compared to .4 mm throughout for the Kastle, but Stocklis do not have a cutout. Suspect roughly equal inertia and flex, achieved different ways. The real difference between the skis will be feel - both are silky but Stocklis generally have less snowfeel, seem more utterly impervious to what's underfoot, the MX series would be a better comparison if they made a 95 - and I'd guess the SR has a slightly higher top end, although both are very secure skis at speed.
Personal preference more than differences in performance. This is like picking between a 911 and a R8.