While there are multiple rich data formats, Google for the most part seems to be recommending the
Microdata format although, they still seem to support some of the other formats. How long they will continue to do this for the other formats is unknown.

This generally means that if you're going to choose a rich data format then, you should probably go for Microdata.
While Microdata doesn't have a direct influence on your rankings, it can help to drive clickthrough rates as potential visitors will see the extra information which is presented by the search engines which support them and they are supporting more and more of these Microdata formats over time.

It's somewhat likely that more and more weight will be given to the Microdata formats over time and it's useful to get used to them now before they become too important in order to make sure that you aren't caught off-guard. Will they be important forever? Probably not, search engines are always evolving, however they seem like they will be fairly important for the next decade or so unless, there's a major breakthrough in search engine technology.