RSS is specified using XML. I do think RSS is more common than Atom though, although most readers will do both. RSS is probably more popular today

RSS by far.

I do think RSS is more common!!

For publishers, it doesn’t really matter, about every reader of significance supports both RSS and Atom. Both are formatted in XML.

Also, “using RSS” can mean “using RSS 1.0”, “using RSS 2.0”, or another version. I do believe of those 2.0 is most common nowadays.

As a reader, when I have the choice when subscribing, I usually choose Atom, but not for a really good reason.

Oh, and also, how is this about micro-content? (What is that, anyway? I suppose you’re referring to microformats? If so, it has nothing to do with it, unless you’re referring to hAtom.)

@Talus057 I’m curios as to where you base that on?

RSS.