I have seen all four broken, how normal the use, well it depends, you are not going to break any of them by chopping a piece of wood.
Mission's A2 snaps fairly easily it doesn't have great flexibility or resistance to impact, I gave it a few shots with a hammer and it cracked in half readily.
Mission's Ti is just insanely high in resisting impacts, you can actually cold work it with a hammer and it won't break, it also takes really high flexes before it will tear, however it will take a set fairly easily (compared to steel blades of the same thickness) and the edge will indent readily on hard objects, the serrations can turn on hard knots.
Strider's ATS-34 blades are very strong, but have little flexiblity and the edge will chip readily and don't respond in the same league at all on hard contacts as the better carbon steels.
I watched a Basic #7 from Busse resist the hammering, banging and throwing of my silverback brother for a long time before it broke (long as in a year+ of the same behavior and enough wear to turn it into a Basic #5).
I had a Extreme Judgement's edge ripple on just knots, but it was very thin, however the edge chipped readily on hard contacts, similar to Strider's ATS-34.
-Cliff
