Reeroits closed source,discord permissions is acl
worse voice quality than mumble,
way more resource intensive than mumble,
funded by tencent (chinese govt),
doesnt have acl,
probably is selling/will sell your data in the future
also voice quality you really can't distinguish unless you really pay attention
also it's resource intensive because it's an electron app, which allows discord to have all the functionality it has
it's made for more than just voice, and if you need something for players to interact with other than just voice, discord still leads. It's not a bad platform, it's just for players who "care" about the little things, mumble will be there for them.
Have you used mumble? The voice quality is 100% distinguishable. And yeah it's cool that you can chat with each other on discord but you aren't chatting in the middle of a scrim/official.