>>19723420It's the little things, honestly mostly stuff you only notice if you have particular setups.
For instance, Twitch forces a pre-roll ad most of the time by splicing it directly into the stream HLS playlist. If you don't have adblock, you probably wouldn't know or care, since you are used to ads anyway. There is no such issue on Youtube.
Youtube also transcodes all streams instead of just ones for partners or with enough viewers. Youtube also has a much, much higher bitrate cap allowing for much higher video quality if taken advantage of. Things that the streamer has little reason to care about, but are very nice for the viewer.
Likewise though if you are a viewer that likes to actually use chat, Twitch would probably feel nicer, more responsive, and has some extra features to get that bit of a rush when using it. I am sure there are other things for Twitch as a viewer, but it's been a diceroll for me on whether the site loads pages properly or not for years now, even with umatrix and ublock completely disabled. I'll chalk that up to my own setup regardless though, as I can't imagine something like that would go without major complaints if it were common.
That, combined with the pre-roll ad that even streamlink can't fully get away from (it just doesn't show it but still requires you wait it out), makes me just not bother watching Twitch streams.