I have several EOTechs 512s and have in last year moved to using Aimpoint T1s instead. I definitely like the T1 much better than my 512s. Many of the pros/cons have been discussed in this thread, but the biggest things for me:
1. The EOTech 512 is heavy! You put that out front on an AK or an M1A, and that is not pleasant. It is usable, and if you have nothing better, you make it work. But the Aimpoint T1 is in a totally different category, suddenly the rifle is a lot easier to bring up and use naturally. I cannot say enough about having a T1 on an AK gas-tube mount, or an M1A scout mount, or even just out front near hand-guard on an AR. All places where I had EOTech 512 and now run Aimpoint T1.
2. I have had A LOT of problems with putting EOTech 512s away with high-quality AA batteries in them, and having the batteries rupture and corrode. This happened on a number of my sights, and they were in a safe with anti-humidity heaters and all that, and they corroded the inside of the sight. EOTech did send me "rebuild" kits for the insides, and I did get the sights working again, but what a pain. And the idea of pulling out a rifle when you need it and finding that it is dead and that replacing the batteries WILL NOT fix it is scary. Now I store all my EOTech 512s with the batteries OUT of the unit, just in case. My Aimpoints have the batteries in them, no worries and no problems, I've had a year and a half to see.
To me those are the two major factors that really make me lean towards Aimpoint.