YouTube’s gaming vertical is 3x bigger than Twitch by audience size, and 4-5x bigger by # of creators. That’s primarily driven by on-demand viewing and the demographic differences between people who watch live (older, grew up w TV, watch passively) and people who watch VOD (younger, prefer to watch what and when they want, prefer personality-driven content, etc).
Twitch is big and buzzy because it was VC-backed and acquired, but YouTube dominates gaming media.