The rule used to be "if you have to ask if the 18 DIN is right for you, the 18 DIN is not right for you"
Now it seems to be "if you want to use 8 DIN or higher, go for it"
I'm not really sure which one I agree with. They're extremely good bindings, if you don't mind the weight and cost then they're bulletproof and have one of the best release mechanisms in the game.