Vanguards at ArenaJunkies posted this nice summary.
“BGs: 25% EXP per win, ~40% from AV win. You also get a box that if you save til level 110 you will get 110 gear from.
Skirmishes: 26k exp per win, ~13k per loss. I averaged a level every 45minutes or so playing Ret double dps 2s”
I personally won’t run AV. It often takes “forever” and you might not win. I prefer the shorter duration BGs.