Based on the stated requirements, it was always going to be Nashville, Raleigh, or Suburban Atlanta, IMO.
Raliegh has decent air service, decent weather, and low taxes, as well as cheap property values ( compared to Seattle).
And it does not have an oppressive soak-the-rich tax like Seattle, either.
Most importantly, Raleigh has the Research Triangle
“Raliegh has decent air service, decent weather, and low taxes, as well as cheap property values ( compared to Seattle).”
Raleigh metro area also includes the Research Triangle Park with a number of tech companies. There are also major research universities (Duke, University of North Carolina, North Carolina State) so there is a strong local hiring pool to staff the organization at the new headquarters. There are many progressive intellectuals in the area.
There is passenger rail service from Raleigh to Washington DC, Florida, and North Carolina’s largest city (Charlotte). The state has a variety of recreational opportunities within an easy drive (mountains, coast, lakes) as well as fun cities for weekend getaways (Charleston, Washington, Richmond, Atlanta, Charlotte, Asheville). Raleigh has an active downtown with the restaurants and pubs millennials crave. There are downtown apartments and condos. The airport has been recently modernized and expanded. If Apple and Amazon both come to town it can handle more flights.
The politics in the state are shifting blue. The governor is a Democrat and Democrats control the major cities in the state. Both Republican Senators are “moderate” and are elected by small margins. As the population of the state becomes more urban Democrats will likely take control of state government and the majority of the congressional delegation. Tens of thousands of retirees from northern states are also contributing to the political shift. Amazon and Apple no doubt are looking at the demographic trends and know a move to Raleigh will only accelerate the change in the political environment.