I still self host my TS3 for my nerd herd, and as an EvE online player (currently trying to win, but thats hard), you have to be fluent in all voip solutions as they all have different requirments and say a lot about your group.
Discord - small group, utilizing free services, may have an auth tool, used to keep in contact with people from old groups. Remember kids, if the product is free, you are the product
TS3 - mid-sized group (100-1000 players) requires a real IT team, will have an authentication system and generally will have their shit together. Ease of set up is handy, but admin user accounts can break servers.
Mumble - Welcome to the big leagues. (1K+ players) The resources you require now require resources in meat-space and are rather substantial. You need real IT security and people on a payroll. It will drive your admins nuts for about a week setting everything up, but once its done, you wont have to touch it again.