Incidentally, the alliance are the main PvE faction, with pallys, so by default they automatically become the dominant PvP faction since they are the ones that have an easier time getting a full a epic set. The majority of the Horde in classic can usually only get as far as the rank 10 blue gear and even then, depending on the population of server, it was difficult to get.
Not so much now with BC, is it alliance?