Mixer is actually higher quality and less delay 90% of the time. It also seems to load faster on my mobile data versus Twitch... probably superior compression technology; I don't know. It's more gaming focused and seems less toxic. When I start streaming FPS games again I might quit Twitch as well and focus on Mixer.
This is a great sign for Mixer and Microsoft. Microsoft is agressively expanding their gaming businesses with stuff like Mixer and Project xCloud, acquiring/opening dozens of new game development studios, and doubling up on Game Pass for both PC and XBOX.
Competition breeds breakthroughs. It's never been a better time to be a gamer.