Discord or TS3

Both have advantages and disadvantages. All-in-all, I believe Discord offers some great out of the box features, setting up a server is stupidly simple. However, while TeamSpeak 3 is a PITA to set up sometimes, it has great addon hook support for games. One TS3 addon I can think of is ACRE for ARMA 3 which uses the plugin to simulate military radio communications and implements static, and dynamic signal loss, echo based upon the player's surroundings all through the TeamSpeak client.

tl;dr - Discord for general purpose chat, TS3 for anything more sophisticated