Robert_Charlton - 5:22 pm on Jun 4, 2013 (gmt 0)
For some background on the various structured data formats, and how Google and the other major engines came to settle on microdata and schema.org, this discussion might be helpful...
Ways of marking up a page for a Product
Going forward, schema.org is the microdata format that will be supported by the big three search engines, but you can keep what you've already done in the other formats mentioned....
The thread briefly compares microdata and schema.org with RDFa and microformats, and differentiates these from the Facebook Open Graph Protocol.