Twitch or youtube ?

It all depends on what content you are looking for.
Twitch is still the leading platform on live content while youtube presents you with a whole variety of content
Some things you might want to know:
Twitch is in a confort zone, no one can rival the live content at this point, support and discoverability is second to none, its almost impossible to succeed unless you find a gap in the content and exploit it, with a... little luck and help you can maybe make it.
Youtube in the other hand, its leading every type of content besides live streaming, it has massive discoverability potential and it has all the tools to improve and lead everything in the market, forcing twitch to move and pay more attention to its creators.
So, long story short, unless you want live content, youtube is the way to go, also,... if you are looking into get ting in the content creation, you might consider give it a try on youtube.