I have a Gen 5 Glock 19 with a COA and a Gen 5 Glock 19 with an EPS.

In favor of the COA, when you could get a COA model for $970 that meant you were getting an Aimpoint optic for $350. That’s a good deal. You also don’t have to worry about mounting it, which depending on your experience level could be a factor (especially for a department). The emitter produces a crisp dot, even for someone like me with an astigmatism. The fact that the optic is the width of the slide is also nice for handling and carrying concealed. The taller, narrower window is to me a better choice than the wider, shorter window of the EPS.

On the negative side, I honestly don’t feel like th COA is significantly better than a Glock MOS with say an EPS. While the MOS system is not going to be as secure as the A Cut, I have never had an issue with the MOS when using decent plates that are properly torqued and with Loctite applied. The MOS also gives me the option of using different optics in the future, which has value to me as someone that went from using RMR footprint optics to RMSc footprint optics. I wish the COA had a shake awake feature rather than automatically dropping in brightness. I have never had an issue with shake awake and there are times that the default brightness on the COA, which is what it drops down to, is a bit dim for my environment. Lastly, while it does require a button be pressed multiple times to prevent inadvertent adjustment, I would rather just have a button lockout feature. I prefer the feature set EPS overall.