So long as the code isnt full of errors, will it make any difference so google (or any search engine) if my site has a HTML or xHTML doctype? thanks
i think too there's no difference, it's not the site type or extension, it's the contents, clean codes, structure, metas, etc.
Im unsure too but one thing I know for sure is that i prefer to code in xhtml and validate so the coding is clean and easy to work with. It also is better to use the newer xhtml for the fact that it is more future proof.
It makes no difference at all. There are debates around whether it is best to sue HTML or xHTML, but these are not centred around SEO. xHTML 2.0, when it is finally released, will not be backwards complaint, so in preparation for this it matters little whether you currently use HTML or xHTML.