I don't think it's a good idea to write the pages in XHTML. I especially don't think that it's a good idea to write them in Transitional. Transitional is, as the name says, for transitioning - for slowly converting legacy pages to modern, lean markup. As such, it should be avoided for new pages - they should be modern and lean from the start. Strict is the way to go.
As for why HTML over XHTML:
http://www.hixie.ch/advocacy/xhtml
In short: Internet Explorer does not support XHTML. Period, no discussion. Oh, and IE7 won't either. So if you want proper code for IE, you have to use HTML, because it simply will pop up a download window for application/xhtml+xml (go here to see the effect; these pages are true XHTML).
You could send the code as text/html to IE (but the SourceForge servers don't let you decide which browser gets what, unless you script it yourself), which means that the browser interprets it as quite horribly broken HTML. Which causes problems.
So go with HTML 4.01 Strict. It's by far the best choice for current interoperable websites.
