Of those three I do best with Youtube. It won't make you a millionaire overnight but the income just keeps increasing because once the vids are up, they stay up for good and don't require any more input from you. Some stuff gets banned but overall I find Youtube is a stable passive income. I've found Youtube traffic in my niches to be extremely high quality and the advertisers love it.
I used to do OK with Twitter but you have to keep constantly working at it to keep the income coming in. It's like you're starting from scratch all the time, plus Twitter traffic is just shit in terms of quality and advertisers don't like it.
Can't comment on Facebook.
SE traffic is of course the best source of traffic you can get and most of my income comes from spamming Google.