I've never ridden STH's myself, but I've seen friends break them from time to time, as well as pre-release in them. That being said, I've never seen FKS's break, even the plastic 140's (besides the breaks, which like to snap off). Besides durability and security, what I believe sets FKS's apart the most is how short the mounting pattern is. Most bindings like the STH's and PX series bindings have a longer heel piece platform that while allowing you to adjust the binding to accommodate several BSLs, usually puts a "dead spot" in the ski because the binding stops it from flexing as much. FKS's however, have a short heel piece that doesn't really affect the flex (The only issue is that they don't have too much adjustability in regards to fitting different boot sizes).