Flex vs JavaFX vs GWT

I want to filter down on one client side technology for my application. How would you rate each one in terms of

1. Performance (light wieght or Heavy wieght)
2. Ease of Use
3. Quality of UI
4. Integration with Struts 2.1

i could have asked this question in Flex forum or JavaFX forum or GWT but then i think i will be able to get a more reliable solution here as i need to understand the integration of this client side technology tool.

Performance is a key issue for me. my application is very much perforamance intensive. and secondly what looks good feels good so the UI components also matter.