Aimpoint sights are generally more robust and battery life is incredible (in many instances, 4 years of always-on). The drawback is that you are simply getting a dot in a tube, and some people prefer reduced FOV obstruction that the EOTechs provide (sort of a "low profile heads-up display vs. a dot in a tube). Many of the older models of EOTechs have had issues with the battery terminals failing, while Aimpoint traditionally enjoys a reputation of building a more durable product. I personally think the Aimpoint ought to be more bomb-proof - it's just a dot in a tube. It
seems to a layman like me that there's more going on with a holosight like the EOTech, and more potential for failure (and battery draw). Also, the EOTech will auto-power-off after 4 hours of use, while the Aimpoint will stay on indefinitely.
AA models of the EOTech are still popular for the reasons you mentioned - price and battery commonality. Small and light is king these days, so used AA models can be found at great prices on the second-hand market. CR123s have become common these days in tac lights, but this didn't used to be so and a lot of guys want to run the same type of battery in their optic as their flashlight.
Get whatever you feel you can shoot best with. For me, that ended up being an EOTech - I don't have to worry about my optic surviving an IED blast, and I have no problem with changing batteries once or twice a year. I very rarely spend more than 4 hours at a time with a rifle in hand, and I prefer the EOTech reticle.
Everyone has different needs and preferences - this is a decision with no one "right" answer. Let us know what you decide to go with...
