You are so right IMHO. If I were going to this event, I would want to park my car and do everything I wanted to do and not get back in my car until I was ready to leave. Charlotte has (by far) more to offer and do within close proximity (walking distance) to the arena than Greensboro has. There are lots and lots of restaurants and bars within walking distance to the arena, and when EpiCentre is completely open you will also have the option of a bowling alley and movie theater, even if they are not mega complexes the option is still there, plus additional retail, restaurants and bars. There's also the option to jump on the light rail line, which is right next to the arena, and go to a number of places south of uptown. This option will only become greater in the coming years. Plus you can count the existing museums with three more to be added soon, and the NHOF. All of this within walking distance, not to mention things I forgot.
For me, the overall experience would matter the most. I think if you were to do a survey of people who have gone to this tournaments both in Greensboro and Charlotte, you would have far more wanting to go back to Charlotte.