I see it differently, James. <b> is for visual presentation only - no change in meaning is intended. <strong> imparts semantic strength to the content (a louder voice, if you will.)
Search engines are doing all kinds of things today, and mark-up like this has a lot less power than it use to. Any time the average website is inconsistent in the technical use of some tag or other, the search engines need to compensate - just as they have for <h1>, for example.