Mia's, Rafa's, Desperados, Matt's, El Fenix -- certainly I haven't eaten all the beef fajitas in Dallas, but I've eaten quite a few versions. I've been looking for perfectly cooked skirt steak, and most renditions I've had have been extremely tough and dry.
See also: - Tasting the Worst Fajitas Ever at Matt's Rancho Martinez - The Nine Best Tex-Mex Restaurants in Dallas
Meanwhile El Ranchito, the massive Mexican restaurant in Oak Cliff, uses a prepackaged, marinated product that ensures juicy, salty meat that's incredibly tender. If that sounds a little too Food Inc. to you, stick with me.
The tender outside skirt we all covet gets exported to Japan, and a recent lifting of Japanese restrictions will likely further that trend. So far I've only found one restaurant that serves outside skirt, but Mi Dia From Scratch covers the grilled meat with an unwelcome blanket of cheese.
The inside skirt we're left with is the source of most of these rubbery fajitas I've been eating everywhere else. Without a chemical bath (don't worry, the stuff is made from figs and other fruit) inside skirt is so tough it will pull right out of your flour tortilla.
At El Ranchito the beef is well-charred and salty, with an occasional tinge of pink that indicates the meat has not been overcooked or sitting around for days. The flour tortillas are soft, fresh and made in house, and the meat arrives with that tell-tale sizzle that announces a steaming hot plate. A steaming hot plate of really good fajitas.