I own a Aimpoint Comp M4, a eotech 512 and a ACOG TA31RCOM4...my opinion would be if you were just going to have 1 of these go for the EoTech. And also think about going with the GGG mount or a Larue I have the Larue on all of mine and love their mounts.
The Aimpoint is shipping out tomorrow I tried to like it but just could not compared to the EoTech therefor I sold it on ebay along with the aimpoint magnifier
The ACOG absolutely has the advantage at 100 yds or beyond, but not quite as fast as the eotech inside of 50 or so yards for my liking due to the 3x magnification, so for general shooting if I had to choose just one out of the 3... I would choose the eotech..Its faster, cheaper, and works really well......but for super high quality and really clear glass the ACOG is the nuts