The AGM 14's will tend to use the exact same format tubes as other retailers' PVS-14s but other retailers will typically use legit milspec housings.
The AGM lenses were sub par compared to mil spec lenses (of those i have used), but I heard the newer ones have coatings to reduce glare? Either way, they are 100% usable.
The AGM / ATN offerings generally suck because the housing electronics are not of the same quality. Both companies also have products that are outstanding within the rest of the lineup, but they also have some absolute shit.
For example - I do like ATN's thermals. I think the image quality on them is actually pretty good for the price. While I've never owned any, I have heard similar about AGM's thermals. ATN's PS-15 housing is pretty lousy. I dont know why they keep buying it from China instead of going with some BNVD-40 option like AGM. The BNVD-40 from AGM is like a Hi-Point pistol. It is a damn brick, but it is built solid and once you work the quirks out of it, it is a quite robust and dependable device.
At the end of the day, i think it depends on your needs, budget, etc. I dont just blanket statement say to avoid ATN, AGM, or Armasight, though.