How to get mobile site in Firefox to be displayed as in Chrome for Android if spoofing doesn't help? On my Android device, while using Internet, Dolphin, and Firefox (left), I see the same version of http://m.chase.com that my desktop browser (right) sees:

  



On Chrome for Android (left), it's different, being similar to what opens iOS browser (right):

  

I want to understand why/how, and then see if I can get Mobile Firefox to load the blue version. I don't think it's the user agent string - I've tried spoofing it already.
Note that both iOS browser (safari) and Chrome (desktop or for Android) are based on WebKit engine. That's why they are so similar in what they render. 

Firefox browser uses a much different engine: Gecko.

As an answer for what you want to do, I think that given the CSS and javascript the mobile site loads is different depending on the rendering engine, currently it is not possible to an end user to achieve that. A better design must be done by web developers who made the website, in order to avoid this kind of awkward situations.

If what you need is to open that mobile site with a browser different to Chrome for Android, but that it be rendered the same way as Chrome for Android does, I recommend you to use Opera Mobile or Opera Mini (based on Presto engine), here is a screenshot of how it looks there: