Glock Factory magazines vs after market?
I remember almost 20yrs ago a company called USA magazines, and after the first Assault Weapons ban, that was about the only manufacturer I knew that made 30rd magazines for the Mini 14, but I had really bad experiences with them. The majority of the problem was with the followers and this seems to be a pretty common issue. If you move machinery from one location to the other and have any minor changes in the equipment, that slightly out of spec magazine is going to jam up in your firearm and that is pretty much what the problem is with after market magazines. I have not the time or the energy to test out after market magazines because I actually started using them and then learned to only buy Factory mags but now that there is another run on firearms and magazines, some people are tempted to buy what they can.
Should you bother putting your money into something that is not a factory item? If you don’t have any other options a brand like Promag magazines 
has a pretty good reputation and some of our customers have told us that they use them in their AKs and or in the Walther PPK or Ruger LCP we can give you that. There’s nothing wrong with having a bunch of magazines that are in your range rotation but for primary use, i would stick with magazines that have been tested or just stick with Factory magazines. Many companies stand by their magazines and have warranties so also do some research into that before you buy.