Viewsonic has announced the ViewPad 10 Pro, a 10” tablet that runs both Microsoft Windows 7 and Google Android 2.2.

I saw the ViewPad 10 Pro briefly this morning here at Mobile World Congress. Specs include Intel Oak Trail chipset, 2GB RAM, 32GB storage, and front-facing camera for conferencing.

The big appeal of the ViewPad 10 Pro, successor to the ViewPad 10, is that it runs Android as well as Windows. Just tap a button, and Android appears in place of Windows.

Sounds good; but as Viewsonic explained how this works I became doubtful. Apparently Android runs in a virtual machine on top of Windows. I have nothing against virtualization; but this approach does suggest some compromises in terms of Android performance and efficiency. No matter how clever Viewsonic has been in its implementation, some resources will still be devoted to Windows during an Android session and battery life will be less good than it might be.

I can see more sense in running Android first, for the sake of its speed and efficiency on low-power hardware, and Windows in virtualization for when you need to dip into Excel or some other Windows application.

The upside of this approach is that you can switch between the two without having to to do a hard reboot.

Viewsonic says you will be able to get one of these in your hands around May 2011.