Facebook’s platform can’t be directly compared to OpenSocial. Facebook is a closed set of technologies and formats defined by one company. Google’s OpenSocial is a standard defined by Google in collaboration with many companies. In general though, it is useful to understand what subset of functionality is covered by the OpenSocial standard.
Here is a quick chart that I created for a presentation at StartPad last night.
The main message last night was that OpenSocial is not ready for prime time, and probably won’t be until early next year.