I don't think you can go wrong with either choice, I've never heard a bad word about any of the Aetecs or the Burris FFII, but I've not heard anything about the IR Aetec, so you're on your own hook there. I have a 3-9x40 FFII with the Ballistic Plex reticle, if I were going to recommend any Burris, it would be that model, great glass and priced right.
Tim