On most websites, I use headings on a page (typically H2) for distinct sections – not only within the main content, but also for sections such as "Section navigation", "Page tools", "Footer". (Usually invisible via class="visuallyhidden".) This is a well-established accessibility technique – making it easy to navigate between landmarks on the page (In future I may use ARIA rel="landmark" for this).
An SEO agency has advised our client that these elements should be changed from H2 to DIV, "because they are not semantically relevant compared to the complete page content (and keywords we decide to use)"
I want to advise our client that the accessibility benefits outweigh SEO. Who is (more) right – me or the SEO agency?