I think the KC777 might have been a good tanker / transporter, but not for this requirement. I heard a fully loaded 772LRF needs 11.000 ft of runway at sealevel (can anyone confirm) while the USAF requirement is 7.000 ft.
Some basics from Seattle Times (know for great illustrations):
as for the rest most people seem to agree the KC30 is the more capable option.
It seems to me the USAF is adding an awfull cargo / passenger capability to its tanker fleet. 32 pallets 4000nm non stop is serious.
I wonder if they will sit in the desert as much as the KC135 during the last 40 yrs, or the USAF will put them to use.
That could IMO mean bad news for follow on C-17 orders and civil contractors..