There's a few things to consider, namely, the size of your target.
A man sized target @ 300m is about the size of the front sight post on most mil spec/standard iron sights. It can be challenging to hit but certainly doable.
1x of mag per 100 yards has always worked for me personally; keep in mind optics will tend to lose clarity as they're cranked up.
The nice thing about the EOtech is their reticle setup. Their (~1/3) 1 MOA dot is roughly the size of an inch at 100 yards, 2" at 200, etc so it works well on chest size target in the higher ranges for the 5.56. The 65 MOA donut helps in range estimation and can be handy in up close and personal situations. (65MOA is about 32" at 50 yards, 16" at 25, etc)
I debated going with a DMR 1-4x, ACOG, or EoTech's FTS Magnifier for my old school 512 and decided to rock the FTS Magnifier as I'd come to like the EoTec over the Aimpoints on my deployment.
The largest drawback of it is twofold:
1) No space, for anything. I have an old 512 and with the magnifier, there is no room on my top rail for backups like before.
2) I'm completely dependent on batteries. What can go wrong usually does.
3) Lack of easily establishing BDC
If I were to do it all over again, I'd probably use the XPS-3 with their BDC dots.
While the sight picture is clear and decently bright, it is hard to argue against an ACOG or DMR optic with 30mm tube and decent exit pupil size. The eye relief is kind of short, so you have to adjust when switching over.
My brother recently bought a Millet DMS 1-4x to test. While the quality was on par with 200$ optics, it's actually not a bad buy. Nikon also makes their M-223 1-4 optic that is a decent buy as well.
Overall: think of the targets; consider the subtensions of the reticle, and plan for the inevitable dead batteries.