Buying used, Aimpoint over EOTech. The old EOTechs had a lot of issues (delamination, fading, lousy springs in the battery case, etc) and cannot be repaired. At best, you'll get a 50% off coupon from EOTech which will allow you to pay full MSRP after buying a lame used one.
New with the 10 year warranty? EOTech hands down. Love my Aimpoints but EOTech has them beat in every way. Hell... I'd contend even with respect to battery life. In the Texas sun, I need to use my optics at/near full brightness. Using the EOTechs 4hr automatic shutoff, I've never, over a decade of shooting regularly, had one come out of the safe/case that wouldn't finish the day. My Aimpoints come out of the bag dead every now and then, though, if they get packed without being turned off. Operator error, granted, usually from friends helping pack, but something that happens exclusively to my Aimpoints regardless. Their 50,000 hour estimate is for a brightness level I cannot see outside and plummets to what feels like a week or two at a full burn which goes fast when they're active in the safe. PRO and ACO are also going to need batteries you won't have for anything else.