I prefer the forum, personally -- Discord feels chaotic to me.
Maybe I'm just too old. The last game I played with any regularity was Doom... ¯\_(ツ)_/¯
You know what, I've grown to like Discord. Top tip: as soon as you sign up, change from the default dark to the light theme. It makes it feel less like a gamer hangout and more like a standard chat app.