These frameworks typically just allow you to wrap native methods with JavaScript... so you're not really writing to a single cross-platform code base. Morever, if you can build your app entirely in the HTML/JS/CSS side of things, you're golden... as soon as you start to bridge between the Native and JS layers, things get messy (and often very slow).
Are you just talking out of your ass? Have you actually built an application using Ansca Corona, Ruby Motion, or Appcelerator Titanium? Have you built a published native and Phonegap app to the Android or iOS store? Well, I have done all of these - and I even speak about it at conferences[1][2]. I can safely say you have no idea what you're talking about or you are pushing a hidden agenda.
[1] http://lanyrd.com/2012/lone-star-symposium-austin/stbht/ [2] http://lanyrd.com/2012/uberconf/stcdt/