I went with the AA. for a few reasons
1. I read good things about them here
2. Mil spec forged lowers
3. AA has not increased their prices, you can still get a stripped lower for $100
4. lifetime of the weapon guarantee
EDIT: well i guess they did raise prices $30, read their home page, he says it better than i could. Still top notch.
Down side is in reality you are looking at 6-8 weeks before you get it. But for me the above out weighed the wait. Not to mention i was not going to pay $2-400 for a stripped lower, Everything is back ordered these days anyway. I just made my order last week so i haven't touched anything. But i put a lot of trust in what people had to say here, i got 4 complete lowers and 1 stripped lower.
I dont know enough to comment on the SLR
good luck