anyone can get an ACL tear it all depends on how you fall but if your spinning off kickers and charging all over the mountain at warp speed your going to increase your chances.
as far as the bindings go - what version of the fks are you looking at; the 12,14 or 18?
the 18 is super burly with a full metal housing, and has a bit of a cult following as well. then the 14 doesn't have as much metal just the heel piece i think? and the 12 will be new next year.
the problem with the fks (no matter which one) is the brakes, if they snap you will have to send it away to the manufacturer to repair as its not just something your local shop can do and this takes time.
apart from that they are some of the strongest bindings around.
i don't know much about the axial but i would strongly recommend the salomon STH driver2. they come in 13 din and a 16 din versions (16 being all metal) but what i like about them is that they are very reliable and if something does go wrong theres loads of spare parts available so its quick and easy to fix. they have lots of adjustment too so you can get a really solid fit.