Well, the mobs in Outlands actually give more xp then the mobs of equal level in Azeroth. that being said, since you're already getting the RaF bonus and (if you have at least 3 toons) the party bonus, I'd just stay in Azeroth and knock out a couple quests.

Since you get the 3x xp on quests, you'll be 60 soon enough. Then go to Outlands and kill mobs/quest out there as both the mobs and quests are worth more xp and you won't have the RaF bonus anymore.