I've done both boosting with RaF and questing with RaF and I found that questing wasn't that much slower if you were smart about which quests you took and the order in which you did them (especially now you can get land mounts at lvl 20, and epic mounts at 40).

The other benefit for questing over boosting is that you can level gathering professions without slowing you down too much.

Cheers,
S.