I don't know, and most of the articles that turn up on a quick search are from the very launch of YouTube Red, so their speculation may not have held up in practice. My understanding is, creators get more revenue from Red viewers than from ad-backed viewers. However, I also support many of the creators directly on Patreon, and YouTube itself provides value to me which I don't mind paying for (high quality and actively developed app; decent discoverability features; bandwidth ain't free).