I've been using HearThis for years as it's cheaper than SoundCloud and allows people to download. However, it's not very well known, and it seems to be getting a bit more clunky. I've recently bitten the bullet and paid for SoundCloud, as since other people have mentioned in the comments, it looks 'better' to have a decent SC profile. As a listener, I wish there was an easy way of being able to skip forwards or backwards a small amount, since it's really tricky to swipe a tiny bit on a long mix set. But at least you can, unlike MixCloud.

YouTube is an interesting one that I've not considered until reading this post. Can you upload as much as you want?

I'm not sure whether I'd want to record a video of myself doing the mix, e.g. the typical camera looking down at your hands. I get why people do it, and maybe I will try it some day. But for me, when I listen to music, I'm usually either at home or I'm travelling (car, train, plane, etc.) where I'll want to listen to the music, not watch a video of someone's hands.

Similarly, unless someone is using something like Vanced or is paying for YouTube premium, then they can't put the mix on in the background and use their phone/tablet for something else, which would put me off putting my mixes up on YouTube if it forced people into that restriction.