XHTML 2 and HTML 5 are two markup languages, one used to represent documents on the World Wide Web and the other is an improvement on the first, allowing for content not easily represented. XHTML 2 is the type used for documents, obviously documents are not the only thing it's capable of representing but it's what it was primarily created for. HTML 5 is the upgrade, meaning it can handle the document type content of XHTML 2 as well as non-document types of content.
With these differences in mind, I feel that the HTML 5 is a much better markup language when compared with XHTML 2. First, the World Wide Web is a place of new information and constant change. It is dynamic and constantly improving in its complexity, not to mention diversity. Some of the noted types of content XHTML 2 has trouble with are forums, auction sites, and search engines, and we can all very quickly think of several sites that fit into one of those categories. As they are some of the most popular sites on the web, with an easier markup language than has been available, ideally we as users would see more user-friendly auction sites, search engines and the like. It would of course make things easier for the developers and creators as well.
One thing that seemed to be a very good feature of HTML 5 is the uniformity it would bring. Users of XHTML 2 have lots of room and flexibility with the language, which has benefits and negatives, when others try to use or modify the content of another developer. HTML 5 has more strict language rules and this should help the overall conformity and universal format of each developer's content. These are all the reasons I feel the move should be made to HTML 5 as soon as possible.