I am looking for a nice fast prime. I am mainly going to be using this for concert photography as a hobby. I see most people love their "nifty fifty" but it seems a majority of users are using crop bodies so 50mm is roughly the equivalent of an 80mm lens on a full frame body. I am torn between the canon 50mm and the 85mm. Anyone with any experience with primes for concert photography have any opinions as to which would be a better option? I currently have the 5d MKII and canon 16-35 2.8L II, 24-70 2.8L and 70-300 2.8L.