For my money between those city pairs I'd probably go PIT-DFW-LAS on AA as long as that was a legal connection. I like the newer style AA F seats, (pictured below), as the butt slides out when you recline. Plus with AA you're getting decent meals, wifi and power. Now, the seat pictured is on the 737-800s and some 757-200s but NOT the MD-80. However, while that one is older, I still like it too: