Micro–semantics today (my take on things):

• RDFa: Great for capital-S Semantic Web people
• Schema.org: Way for SEO people to suck up to google (satisfaction not guaranteed)
• Classic microformats: widely implemented but confusing and verbose at times
• microformats-2: the solution

Disclaimer: I don’t have extensive experience with RDFa or non-schema.org microdata. I can neither confirm nor deny knowledge of volcanoes with fax numbers.