Too hard to decide, I think tactically 51st could win, when I was playing for them I found they camped quite often and their shooting ability was real good. Melee wise there was little skilled players.
I think 47th would win this one, if 51st stayed in the community a little longer 51st would probably have been able to defeat 47th. But I vote 47th, their individual player based skill is more superior imo.