Discord has many more features and options. For instance on steemit chat, there's only one room to a channel. On discord, you can have different rooms. So you can have a separate room for post-promotion (link-dropping). You can have another room for admins to talk in private. You can have a general room for everyone else. You can have admins and moderators and members and regular users, all with different access rights to control the channel. Etc.