How do you mean?
Are you doing this for achievements? For cosmetic rewards? For character-enhancing rewards?
If you mean you want to know which factions you need to boost your stats (basically, enchants), then you want Sons of Hodir and Kirin Tor (both assuming you will be gearing for PvE). But this only matters if you DO NOT have a character on the same server with them at exalted. The enchants themselves are now BoA, and can be transferred cross-faction.
As for item rewards, I'll leave that to someone else. Most will probably be replaced through badges fast, though.
____________________________
IDrownFish wrote:
Anyways, you all are horrible, @#%^ed up people
lolgaxe wrote:
Never underestimate the healing power of a massive dong.