OK, I've used the Aimpoint, the Eotech and several versions of the ACOG (including the TA31DOC, which is basically identical to the TA31TRD).
I use my optics as general purpose, meaning I use them for everything from 6" plates at 300yds to NRA targets at 600yds, to firing multiple shots on multiple targets while moving at under 15yds.
My primary optic is the TA11. I use that because when I bought it, the TA11F was not widely available; but the chevron is probably a bit handier than the donut.
The benefits of the TA11 is that it has a longer eye relief and a larger exit pupil than the TA31 - this makes it easier to get good hits during dynamic shooting close in and use some non-traditional positions; but the TA11 is still slower than the Aimpoint or Eotech (up to a second slower for me on a 6-shot string of shooting while moving).
The Aimpoint really shines when it comes to shooting while moving or reflexive shooting at close, moving targets and is tough to beat for that purpose. At under 30-50yds, it will run with the TA11 and beat it consistently.
If you plan to shoot 3-gun (or home-defense, LE, or most practical shooting scenarios), then the Aimpoint will generally do better because most of those scenarios will be under 100yds and what little they give up in precision at those distances, they will make up for speed.
The one exception is when we do a "jungle run" with poppers spread out amongst the brush and trees. Even spray-painted whites, the poppers can be tough to see with the naked eye. The ACOG's magnification will let you tell the popper from a light colored tree trunk in those conditions.
Now at first the TRD sounds like the best of both worlds; but in actual practice, the cheek weld for the dot sight is way higher than the cheek weld for the ACOG. Which means if you have any kind of muscle memory built up on using a good cheek weld (and you had better have if you plan to be good with irons or any magnified sight), you end up using the magnified view under stress anyway because your cheek weld gives you the ACOG first and then you go "O yeah, I have to raise my head."
Any of the sights you are talking about is capable of doing anything from 0-300m. They just have different areas where they excel.
One thing I don't have much time with is red dot/magnifier combos, so I can't comment much on those. The few I've seen haven't impressed me in terms of glass and clarity. I also am not crazy about magnifying a 4MOA dot; but they do serve the main purpose of a magnified optic (target ID and acquisition).
Personally, if I was doing it all over again today and picking a new optic, I'd probably be looking at a variable scope. At 1x, they are almost as fast as the red dots. At 4x, they can do what the ACOGs can optically; but they aren't quite as rugged.
If I needed ACOG-ruggedness, I would probably look at the TA33 - less than half the size of the TA11; but 90% of the performance. The TA31 is a great optic; but for my purposes it sacrifices more capability at the ranges where most of my shooting happens for longer range ability.
Otherwise, for a general purpose rifle, some flavor of Aimpoint is hard to beat - especially if movement (yours or the targets) is part of the equation.
Zak Smith has an excellent article on this and I think that article and some other good reads on the subject can be found in the "Rifle Forum Reading Library"
