Grizzly is by far the most recommended campground, for hookups.
inside YNP, for hookups, Fishing Bridge is your only choice and it's tight.
personally, i would never stay there, i'd rather dry camp than be packed in like sardines.
we liked Madison for the west side and Canyon for the other side, but we're used to dry camping.
i'd never stay at Flagg. i chose to stay in YNP, to visit YNP and in Colter Bay to visit Grand Tetons.
i saw no advantage to staying at Flagg, not for location, price or reviews.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC