Annapolis is really cool, and in sort of an isolated way (ie, you really don't want to live in Annapolis to work in DC). Great culture and USNA, access to the bay, eastern shore, and ocean is good other than the bay bridge. But really not great if you're coming to DC every day.
Fairfax is populous but not crowded, economically prosperous, and pretty much the definition of an exurb these days. If you like driving among massive cloud data warehouses and AMZN distribution centers (at least in its outer reaches), you'll love it. OTOH, good proximity to city (with Metro actually opening someday out there), international airport, the beach, and the mountains.