I've been coding for a while and it's just struck me, what's better to use in terms of SEO:
According to Matt Cutts are treated exactly the same. FYI,
<em> are also treated the same.
John is right, but
<b> denotes the way it should look like instead of the meaning like
<strong>. The same with
<i>, you are saying that text should be in italics but, with
<em> you are making emphasis on that text.