I Glock still making them the way they used to? We used to have officers come through with 10 rounders during the ban and I don't recall any specific problems. We regularly dropped them on concrete during training.
Because of their translucent body, the ETS mags let you see how they decrease capacity to ten, and it looks sketchy to me. You can see where my concern arises by looking at the photos in the link:
https://www.etsgroup.us/ETS-Group-Tr.../glk-17-10.htm
As you can see, rounds are kind of cock-eyed to one another, I'd describe it as going from semi-single stack at the bottom to semi-double stack at the top. It looks from the pictures as if the rounds 'pivot' around a rib in the magazine body. I like ETS mags, all I use in my action pistol Glock, but that 10-rounder is one mag I would have to use under all conditions before I'd trust it.
I do not know how Magpul does theirs, but unlike ETS, they:
Utilizes the same double stack feed geometry as the standard capacity PMAG GL9 to ensure feeding and to avoid known reliability issues seen in many competitor products on the market.