As a user, I prefer YouTube, and it’s for only one reason: They accept Google Play credits for Superchats, so I can donate to streamers if I so desire, and not if the credit card desires.
However, when it comes to which I would prefer if I streamed myself, I think I would go with YouTube, as they also have countdowns to when the stream will start. Correct if I’m wrong (because I don’t go to it that often), but I don’t think Twitch has countdowns for when the stream will start (even though they have notifications for when it has started.
Overall, I wouldn’t mind switching to Twitch though. Seems decent. Prove me wrong.