I'll pitch in on behalf of Sencha Touch!
Speed
So much in Sencha Touch comes down to knowledge of the framework and acknowledging you're coding an application and not a webpage. That said you can get fantastic performance in Sencha Touch. A lot is made of Sencha Touch not being open source but that's a technicality. You can see the code and it's incredibly well documented. I'm delighted with the performance of native-like components like lists and forms that I can achieve.
Native Feeling
This is surely where Sencha Touch has the best edge on its competitors. It comes with themes for ios6, ios7, android, blackberry and windows phone. So your app can look native in each platform. Sure, it's still up to the dev to handle different expectations of, for instance, touch gestures, and the troublesome Android back button, but the framework gives you all the help it can. People don't know the apps I make in Sencha Touch are HTML5 - they look and feel native.
Development Difficulty
Anyone can just start with Sencha Touch easily enough but you will need to be prepared to invest time in understanding how to get the best out of the library. In one sentence: "minimise DOM interactions". In particular, learning that changes to models/stores linked to the dom will automatically trigger DOM updates.
Documentation and Community Support
Fantastic. Because I for one prowl stack overflow helping where I can ;-) the Sencha forums are a great place for support. The documentation is definitely the best I've ever worked with.
Hope this helps you in making a decision! Modus Create did a great series of articles on their blog comparing all the frameworks too (scroll down past first couple of posts): http://moduscreate.com/blog/