Levels >> AA's
Climbing in levels gets you more hitpoints, more mana, a higher damage table (just ask any DPS melee), higher stats, resists, skill levels and in some cases better stats on your gear / reaching the required level of that gear. Etcetera.
Now, before you start waving the index finger and telling me that "there are certain priceless AA's every class should have as soon as possible" : yes, I agree. But for me, playing a rogue, every DPS increasing AA was merely a small 'upgrade' compared to the raw power my character received just by leveling up.
Also, I don't know about you, but when I am building a group, the first thing I look for is people who are level 70. Do not underestimate the first impression people get from you just by judging your level. I probably wouldn't even bother inviting an unknown level 65 slower, even though he might have had 800 AA's and rocked as a player.
Some random thoughts :)