I've got an Aimpoint Comp ML2 and love it, it's really personal preference though. They are both great sights, In my opinion the Eotech with the 65MOA ring may be more preferable in a combat/tactical situation. I wasn't real crazy about the pixelated image in the Eotech though, I guess you get used to it.
Aimpoint and never look back. Dot size is your personal preference, in my opinion there is not much difference. I have a Compm4s. It's got the 2 MOA dot and runs on AA batteries. Aimpoint beats Eotech on battery life and you don't have to turn it on and off, just leave it on.
I've been toying with the idea of switching to aimpoint from eotech. Nothing wrong with the eotech, I just like the idea of the aimpoint's point of aim is always going to match with bullet impact.
Aimpoint ML3 2MOA is what I have, the battery life is insane. Its an awesome RDS no doubt about it.
Eotech 512 1/65 is great, took some beat up from me, scratched up and dropped several times but still work fine. Battery life is not at long as aimpoint but AS FOR ME I pick up target faster with Eotech. I love the 65MOA ring.
They both are excellent choice and will do the job. My buddy in 101st ABN said I can't go wrong with ACOG, AIMPOINT and EOTECH.