>Sound quality is literally the same.
no. TS has a superior codec that is unquestionably of higher quality than discord, but that is minimal.
>Ts was superior a year ago and now discord caught up.
TS has much more customization (of server layout and client), is encrypted, has much smaller delay (most VOiP have lower delays than disc anyways), full interface in overlay,temporary channels, icon badges for ranks, passwords for channel and server, is much less CPU heavy, has positional audio, unlimited file trasfer, etc.
Discord is simply more popular because it's design and over simplicity, this is at the cost of all the features that are enjoyable on TS and provide real depth to the software. Discord is nice, but TeamSpeak is objectively better in terms of functionality.