In my experience, I believe that Youtube is the best place to live stream anything. Facebook might have more users but the number of people watching is low. This could be due to the following reasons:

1. Facebook users are NOT there to watch people play video games. They are there to interact with their friends.
2. Facebook is not designed for the gaming streamer in mind.
3. People are trained to go to Twitch and Youtube for game watching.

Twitch on the other hand has the best gaming streamers out there. If you make it at Twitch it could be VERY lucrative. Some streamers are reporting six figure salaries including affiliate marketing products.

Youtube, I believe is the best place to go. Youtube can be just as lucrative as Twitch. If you disagree with me, reply below.