I can't stand Mixcloud man, you can't rewind and their mobile app sucks so bad. Sometimes it just randomly closes and you need to find what you were listening to all over again, it's so hard to find something and there's so little engagement. The time I've wasted with that stupid app while tripping is insane, never have had the slightest issue with Soundcloud.
Music wise it probably depends on what you're looking for, but Soundcloud is just much larger and it's what most upcoming artists/labels... use to establish themselves, just gotta find who to follow.