Livestream because the chat is less confusing and you're able to click links rather than have to manually type them in, (as you cannot right click to copy the link). It was nice to see a larger window of your drawing even while having the chat window open, but Livestream has the full screen function too for users. JoinMe is a great fallback site, but I think Livestream wins the lead.
I have accounts for both, but prefer Join.Me. It's less laggy, free from ads, and user friendly/idiot proof. The only perk I see to using Livestream is the ability to use audio and record sessions. But as I don't use either of those functions when given the option, join.me all the way.