I've been using ReStream.io for 9 months and I love it.
It allows your followers & subscribers to communicate with each other during streams from many platforms.
*Make sure to set up the ReStream Chat so that communication is viable between them.
I don't like the concept of separation and different platforms when you can bring them together simultaneously.
HOWEVER, I do agree that it is more work and effort to keep attentive of both sides. So if you don't have the time to spend on both fronts, then just do the one. Isolationism happens when you aren't as involved in one as you are the other; it's better to focus on one if two are too much of a load to handle.
I keep communication active with both Twitch & YouTube and have a bot (Stream Elements) that interacts with both platforms on either side.
Also, I actually recommend my followers to use both sides, as Twitch is only for streaming and YouTube is for the uploads later, if they want to watch the recordings they missed.
As for upload and latency issues, yes, certain platforms are slower than others - that's just how it is and if people can't stand it, then they can stick to what they like.