In reply to Alecraeside:
I'm assuming from your post that you hire skis.
Ski mountaineering boots with tread on the soles will only fit in ski mountaineering bindings, they won't fit in the hire bindings which are found on most skis available for hire.
Ski boots with DIN (flat) soles will fit in most ski mountaineering bindings or the skis found in most hire shops. The flat soles are very limiting for ski mountaineering however.
There are a few solutions to this...
i. Buy ski mountaineering skis.
ii. Hire ski mountaineering skis (This is only feasible in some resorts).
iii. Use boots which have interchangeable soles. Fitting flat soles when hiring piste skis, and soles with tread when hiring ski mountaineering skis.
Garmont Endorphin, Black Diamond Method, Black Diamond Factor, Salomon Quest are all boots with interchangeable soles. There are probably others as well.
The standard advice is to choose the boots that fit you best.
There are different types of touring bindings, most ski mountaineering boots fit Fritschi and Marker bindings, some boots fit both, and a few boots only fit Dynafit bindings. Most ski mountaineering skis available for hire have Fritschi bindings.