Even valid HTML allows you to use deprecated tags. Why would you use something that's no longer valid in the most recent language. I don't understand what the discussion is here. The W3C has recommended using valid XHTML since 1999. HTML is an old deprecated language whether it validates or not.
I don't know of anyone developing XML right now to work nicely with HTML. XHTML is not much different than good HTML mark-up, so use the best.