Southwest or American Airlines?

OK, so I need to get a new business credit card because I only have american express for my business and not all venders take amex. I'd like to get a travel rewards card. The two frequent flyer clubs I use the most are american airlines and southwest airlines. So which is best? I think I'll use both airlines the same amount since they have different destinations that I need, so I'm thinking that since American Airlines flights usually cost more than Southwest Airlines, that I need to get more miles on American Airlines to save more money? What do you think? Good way of viewing this?
Either way I need some dirt cheap airline tickets now! The holidays are coming up and even though no one is traveling, flights are still expensive!
I am going to check out www.thetravelsteals.com where I typically find the best prices on airfare.