Sencha EXTJS with Desktop Packager or Flex with Adobe Air

Hi. This question may sound a little vague, but just wanted to know if based on your experiance you can provide some suggestions on this.
We are having a requirement to build a very big and Rich UI desktop native application. Also we need live data to be available on application all the time. Which technology would be better to use for such application:
1. Sencha EXT JS and Sencha Desktop Packager
2. Flex code and Adobe AIR.

Please note that we already have full application developed in Flex and running on Adobe AIR. but now thinking about moving UI from Flex to HTML5 and JS as Flex is no longer supported by Adobe. Is this a wise idea?

It seems you have already decided to stop Flex because it's no longer supported. I think your question is whether to use Adobe Air or Ext-JS Desktop Packager.

Though I can't speak for Desktop Packager, I have successfully used Adobe Air with Ext-JS to create desktop applications. I'm not sure what Ext-JS gives you that Adobe Air doesn't from what I can see but Adobe Air is free and Ext's tool is not.

If you plan to move your UI to HTML5, then Ext JS will be a very compelling alternative. Running Ext JS app as a desktop app is exactly what Desktop Packager aims to do. Give its evaluation download a try, it comes with some Ext JS examples packaged and modified to look+feel more like desktop apps.