Grid2 & Mobile

Good day!
Sorry for my English

Faced with the task of automated testing for mobile platforms.
With desktops have not experienced problems.

What is given?
The product - a javascript-engine, which generates a visual representation of the input data, and renders in anything, even SVG, Canvas, etc. though.

What is investigated?
I investigate the behavior of the engine in different environments.
By behavior we mean the percentage of drawing, "correct" image, as well as rendering time.
By environment we mean a triple: OS, browser, browser version.
There are a range of browsers under different operating systems, as the chosen platform: MacOS Lion, Windows 7, Ubuntu 12.04, and mobile platforms (iOS 5, Android 2.3, Windows Phone)

With what there problems?
No problems with desktops. Everything was decided by show of multiple virtual machines with different combination of browser versions. Everywhere configured webdriver all, of course, work through the Selenium Grid 2.

What are the issues?

• What about mobile platforms?
  
• Rising whether all on real devices or emulators?
  
• If you use an emulator, how much difference of ​​rendering time, because the emulator is more powerful than the real device?
  
• If you use real, then we need to create a stand with them?
  
• How it was solved in your company / cases?
  

I would like your detailed (reasoned) opinion on the matter.
Thanks.

In case of Android, I use Android WebDriver - http://code.google.com/p/selenium/wiki/AndroidDriver

Have not come across and discrepancy b/w device and emulator.