In reply to msp1987:
Haven't used either, so can't comment on how they perform. Personally, I prefer gear which is flexible/mulipurpose.
Cravasse rescue wise,over the years, I've acquired: prussiks, a tibloc, microtraxion, ropeman and a revolver screwgate. I've never had to use them in anger, but from practising with them:
-Metal devices are far better than prussiks.
In term of purchases
-Unless you need a motion capture pulley for other stuff (e.g. big wall hauling) it's an expensive 1 trick pony.
-The ropeman and tibloc offer bang for your book, are light, and double as ascenders.
-A revolver caribeener can also be used to reduce rope drag, or as a pseudo-screamer for ice-climbing