The ATACR will have a larger body tube (34mm) and ED glass throughout the entire optic where as the NX8 is a 30mm body tube and has ED glass in just key components. There are several reviews on YouTube that may help you in your comparison.
I some how must have dropped the gun because the top now has a dent. and I dare not try to pull it out so I just skip that rediculous long rubber cap over it eventually I bought nice caos fir it or I used vortex caps. as for the optics 30 vs 34 huge weight difference one is heavier then the gen 3 razor the other is probably the lightest 1-8 in the market around 18oz. but here's where the big things come into play. I love both. one is for my sbr the other for my 18 inch if 16 in..most people do not put optics in snrs that are more powerful then an avog but this not only fits well but it's really good looking on sbrs. the eye box isnt nearly as bad as I first thought. the trick is to get a higher mount one that's atleast 1.7in. most of the time you will not be shooting this at 100 yards u certainly can but there are more reasonable options. this was built for can and basically having the ability to take shots way father then that. I think it's design was ti build a very good clear scope with good dead stop knobs and an AO lock, very nice throw lever very lightweight for those guys who want to replace the Eotech, and 3x mag combination. it's reticle is FFp to get right on targets this isnt meant for sport it's meant to hunt live objects. the 1x is almost true 1 and the reticle is the Brightest I ever seen. it's basically a glorious red dot that can focus 100 yards and give you 111feet a if view. atacre is meant for non sbr and more robust. which makes it a heavy option but the glass is second to none it's basically like a gen 3 razor but the color is slightly better. u can do competition or target shooting with it. because if it's larger AO and eye box. would I want it in Iraq...not really I'd rather the nx8 but in Afghanistan I might want it because you may need to take those longer shots more. the NX8 is really for a very special type of shooting and weapons. if u want the badest 1-8 scope out there that the SF uses then the Atacre. just know there are cheaper options out there that will help you if your in the military then u would need some thing built like this. mrad, it's named after their guidance tool.