These are EXTREMELY different classes lol. Both struggle with movement, though warlock much more so.
Fury has been good in past expansions and even in this expansion, it just isn’t good right now. Warlock this expansion has only had one spec that has been good, and it is very good (destruction). Aff was never very good this expansion and demonology while not horrible, it is also not great. It also is abhorrent to play IMO.
You should pick what you feel resonates most with you.