Originally Posted by VacancyBid

If you're just chasing seniority - EWR and SFO are the places. They're big; they're junior; they have everything.

The full answer you want is complex and time to hold a base vs hold a line vs hold an upgrade etc usually move in sync but not always. Some planes are also different between bases - some 757/767 bases are only 757 and only domestic. Some are mixed and fly primarily Europe with some SA/Hawaii also.

But broadly grouped

EWR/SFO - as noted above - biggest, juniorest, has everything
LAS/MCO/GUM/CLE - 737 only bases. Small. Not for everyday use
IAH - Only hub that is red, warm and no state income tax. Senior
DEN/LAX/IAD/ORD - "normal". suitable for everyday use