I only have Tyrolias on my skis(other than a pair of Dukes going on my 333s). Peak 15s and 18s are the best bindings on the market, and I've owned a few top of the line Solly bindings(my second favorite brand of bindings, S914s/S912s/16s, 914 Labs, STH 16s are all great) FKS(third best, barely behind Sollys) and used non-FKS looks(hate), Jesters(hate) and a few others that were decent. Peaks have the best edge to edge feel, are durable, and have a great low stand height. 15s are 5.1lbs, 18s are 5.6 or less.
NO, they are NOT anywhere close to all metal. They are very hard durable plastic mixed with some metal parts. 18s have metal toe reinforcements that 15s don't, but that's the only difference other than springs.