pro SAN-ORD:

- you can use flagship lounge in ORD as EXP. DFW has only AC
- You don't have to change terminals in ORD, you may have to in DFW
- You can fly premium on 2 class and save your VIP
- ORD breaks up the flight as opposed to DFW being than much longer to/from Europe.

pro SAN-DFW
- Less chance of weather delays.
- You can use your VIP
- immigration line is shorter at DFW in my experience