Youtube accepts a maximum of 9000 bitrate, which allows for beautiful 1080p60 streaming/recording. I've done this myself plenty of times in my previous streams. You don't need to be a partner to have 9000 bitrate as well. In contrast, twitch is 3500 bitrate unless you're a partner.
Twitch always has the 3500 kbps cap even if you are a partner, and if you use 3500 without being partnered a huge portion of potential viewers won't be able to watch because you won't have quality options.
The Youtube player is so much better than Twitch it's unbelievable, there's no additional delay if you pick a lower quality (which makes me wonder if even the highest quality is still being transcoded, much like with regular uploads) and I can switch between the different qualities with literally a quarter of a second pause. All they need to do is not have a shit ui and they might actually scare Twitch into trying a little bit.