IMO the main advantage with FKS 155 or 185 (not the 120 because they have a plastic heel piece and stopper) is that the stopper will never break!
If you lean too much forward when landing switch and the binding comes off, usually the stoppers gets caught in the snow and everything blows up if you have a plastic heel piece. With the 155 and 185 the metal stopper will just bend, not break off.
You don't have to go to the shop for another brake, just bend it back the other way and your good to go on with your day. Really useful when riding the park.
The FKS 155 and 185 are basically bombproof. If you have the money buy them since they will probably last you a lifetime.