can you explain why? I use slack at work and discord at home (for games). I find them to be pretty similar products, except that discord seems more oriented towards voice command and slack seems more reliable and less buggy (on a regular basis discord takes a very long time to connect). I personally prefer slack mainly just because I find the UI more pleasing.
I actually prefer the UI of Discord. I like having all people just listed on the right instead of typing `@` and having to scroll through a list that pops up and blocks the main active content.
I've just seen too many games on slack compared to Discord that I find really annoying, with people being banned and instantly rejoining and flooding crap. It reminds me of EFNET in the late 90s with bot floods and all of the crap that ended up ruining it. It's not nearly as bad as efnet was, but it's still annoying enough for me to not want to use it. That might not be the case for a private company's slack or something, but I'm not really in any of those - mostly public type channels.