In my opinion, TS3 and Discord have their own problems each.
Making Servers: TS3 requires you to buy a server through a third party to chat with friends. Discord allows you to make one for free and is easier.
Roles: If I remember, on TS3 certain roles could be given out by Moderators and you had more control over what roles could be handed out. Whereas, on Discord, anything under the role can be given out if you allow them to manage perms.
In all honesty, TS3 is good for certain situations, and Discord is good for others. I know when I play Island Life on Arma 2, TS3 is the better option. For me, I love Discord for just chilling with friends.