Pete's playing is much more than the so called "Seeger style" of bum-ditty, bum-ditty with the hand suspended and the combination up picking and downward brushes. He can up pick in two and three finger styles and he can down pick in traditional styles as well. Listen to him play Coal Creek March if "lightning fast, hard as nails" banjo is your thing.
Virtuosity is defined as outstanding skill. I don't think virtuosity in a musician necessarily means a proliferation of flaming note runs or extreme technical ability. Technical skill is virtuosity of one kind and on an instrument, may or may not even be "musical".
I do think Pete is a virtuoso in the technical sense but where he shines is in the "musical" sense.
I feel the same about Earl. Just different styles from people with different backgrounds and different tastes.
The musician who can take a musical idea and turn it into sounds that convey that idea clearly to someone else is probably a virtuoso.
Just my two cents.
Chip