YouTube Advantages: Works on a bunch of platforms such as Android, Apple TV, Chromecast, FireTV, iOS, Roku and smart TVs. Different resolutions to choose from. Able to rewind stream.
Disadvantages: ~30 seconds of latency. Currently do not meet the requirements to embed the live stream. Subscribe now and press the 🔔
Twitch Advantages: ~5 seconds of latency with low latency mode. Best quality. Stream viewable in most mobile browsers. Apps for Android/FireTV, iOS/tvOS, PS4, Xbox One and Roku (unofficially with Twoku). Chromecast support in mobile and desktop Chrome and app too. Lowest latency when using Chromecast.
Disadvantage: ~3 Mbps due to no transcoding.