Which Format Should I Choose?
One of the most confusing and unfortunate problems in syndication is the large number of formats in use. In addition to those listed above, there are many other formats (e.g., RSS 0.9, 0.91, 0.92) that are commonly encountered on the Web.
For better or worse, the decision isn’t as critical as you might think. Most aggregators and other software use syndication libraries which abstract out the particular format that a feed is in, so that they can consume any popular syndication feed.
As a result, which format to choose is a matter of personal taste. RSS 1.0 is very extensible, and useful if you want to integrate it into Semantic Web systems. RSS 2.0 is very simple and easy to author by hand. Atom is now an IETF Standard, bringing stability and a natural community to support its use.