I remember being to ranges when I was a kid and seeing the guys with the AR15s and the 3-9×40 scopes and thinking that was the pinnacle of coolness.   If you are target shooting, hunting or on a really tight budget, something like that might be good for you but for close quarters defensive applications, the need for magnification is very low.   Most Police Officers we deal with don’t even see the magnifiers on their guns because many of those guys are even on even tighter budgets.  They use what they know they need and Trijicon ACOGS are something rarely  used in the Law Enforcement community because they don’t need a rifle scope with 3.5X or 4X.  That actually can slow you down with your AR15  or M16 carbine.  The Eotech 512 with the AA Batteries is still the most popular but the XPS and EXPS optics have gained traction because they are lighter and smaller.

On some of my Daniel Defense M4 carbines I am running an Eotech 512 because I find the AA batteries to be more common, but if you bulk buy and stock the CR123 batteries they will work well for you.   Many of the guys running the Eotech sights with the CR123 batteries use those because the weapon mounted flashlights like the TLR1, TLR 3 laser combo use the same batteries so mixing up the battery types is somewhat of an issue.   Battery life can be betwee 600 hrs and 1300 hrs but for domestic purposes having access to batteries shouldn’t be an issue.  Keeping AA batteries or CR123 batteries around is something that should just be as important as having 5.56 ammunition.   If you want magnification you can run a Gen 3 magnifier later.