encyclo - 2:38 am on Feb 28, 2011 (gmt 0)

<code> has specific, semantic meaning that you can't convey or replace with CSS. Simple bolding of text is another matter altogether.

The <b> element for me can occasionally be used as a generic inline container - like span but shorter and with the advantage of having a vestige of visible style differentiation when CSS is disabled. But for SEO, using either b or strong is utterly irrelevant - minor on-page factors such as this count for nothing.