I don't like that IPs are easy as hell to get through it, or the fact that people always get impersonators. The chat is slow with a lot of text/images, and the notification system is either all messages or no messages.
Discord has no IP leak, it's impossible to get impersonators (unique ID), chat is never slow (unless someone spams emojis), and the notification system is channel based, @
everyone / @
here / @[yourname] , or none of the above.
That's just general usage. Voice Chat is higher quality, no disconnects, different servers based on location (that you can set) and there's bots. Honestly, if you're not using Discord in C U R R E N T Y E A R I got no words.