Xml sitemap will better help google discove all your pages. Html sitemap will not be able to let google know about all the pages.
Can you please let me know exactly why Google report the html sitemap as Unsupported file format Your Sitemap does not appear to be in a supported format. Please ensure it meets our Sitemap guidelines and resubmit. What exactly could be the problem as the sitemap one present sounds good Edit/Delete Message There is only Sitemap guidelines for xml...how about Html????