Though TS3 is much better in terms of customizability, I prefer Discord since it's the only "Skype" I have open 24/7.
I can never bring myself to get on TS, ever, it's too much of a hassle even though all I need to do is open the app, then connect. Discord makes it easier, everything is right there. And I don't always want to be connected by voice.
Everyone's different.