Originally Posted by insub2 <b> is depreciated in both XHTML 1.1 and HTML 4.

Since when? If you could cite your source, I might be perhaps a little less incredulous. The DTDs appear to say quite the opposite.

Originally Posted by mikoleg does not matter, both are considered for seo

If your concerns when marking up HTML put SEO (which I believe is a huge waste of time) before correct and proper markup for the document, you're already doing it wrong.