I went blood until lvl 85 and it worked great. Used BloodyMess CC. Frost is the most used I guess but botting with it is hard because you die fast and it's not good looking ending up with 20deaths and 1kill With blood u wont die so much..
So I would say, go for blood (and at the same time u can go dungeons as tank with CLU CC, its awesome).
And when u ding 85..decide what u want to do.....