I think they're both males, because the females are bigger. The males technically can't sting (and the females only do if you're really asking for it), but it's still scary to get up close to one.
The males can be kind of aggressive in buzzing around you but they don't have stingers like the females do. They're big scary looking wasps but pretty harmless. They lived in my back yard for years and no one I know ever got stung by one.