While DFW is a much larger airport, it is not terribly difficult to get around. DFW is a well organized airport IMO. When you get off the rental car bus at the Continental stop in Terminal E, you will have less walking to do to get to your gate, than when you arrive at DAL. I usually take the 715pm flight to IAH and never have to wait for a check in kiosk, and security usually takes only 5-10 minutes. I have found the security lines at DAL to be a tad bit longer at comparable times. Once past security, all of the CO gates are very close by. No need to go very far, and there is a PC and Crown Room if you are a member.

The point about flying a 737 vs a ERJ is a good one. If you are flying to SFO from IAH, try to fly into IAH on a 737. All flights out of DAL and the ERJ flights out of DFW will land you in Terminal B in IAH. Transferring from Terminal B to C or E in IAH is not nearly as convenient as it is at some other major airports.

drnp