These seems to be the next feeds war for the future and this site presents a summarized but good presentation of the feature (and differences) of the 2 standards.
Who will be the winner is really difficult to say now, but I think that RSS (mainly for the large support that it has, expecially from Microsoft and other big companies) could be in a little advantage.
However, I think that all the 2 standards lacks on some features (not present or too poor), for example feed compression and criptography. One thing is not true on this article: RSS 2.0 supports the <enclosure> tag (useful for media contents).
As you can see in the RSS 2.0 specifications, this tag has three required attributes: an url says where the enclosure is located, length says how big it is in bytes, and type says what its type is, a standard MIME type.
The url must be an http url like (for example):
<enclosure url="http://www.mysite.com/mp3/MyAudio.mp3" length="4503865" type="audio/mpeg" />
Correct it please... 