Discord has more easily manageable chat roles, eg: Moderator, Helper, Regular, Supporter, etc. Twitch chat is nothing more than simple IRC, and relies almost entirely on bots for the more complicated stuff. Discord also has voice chat built in, whereas Twitch has none for their chatters.
Discord also has a better documented API and libraries in a lot of languages. Overall, Discord (despite using an electron app...) is simply a better chatting product.