Ate both 5 guys and Smash when I visited my parents in Colorado Springs. Both good, honestly I wasn't blown away by 5 Guys, it's a solid burger joint but didn't stick out as anything special to me. Smashburger was one of my favorite burgers, love the tiny fries (had the kind with some olive oil or whatever, was tasty).
Far from a burger expert (Hardee's is my fast food burger of choice).