If you can babysit it, questing by far. It's killing mobs constantly anyway, and then turning in quests. Once its got the kinks ironed out, it will be by far the best way to go. I do a mix of both, questing when im at the computer, grinding when im AFK.
Also, I like to do the BG CTA weekends when its a big BG like AV, i get honor and exp so fast, I dont even use mixed mode, i just park in the PvP vendor room so i can buy gear to prevent hitting the honor cap. PvP gear is also what I wear when using GB as its full of stam and resil which helps compensate for the primitive combat capabilities of GB.