I've used the LAS many times, DFW once. DFW on a Sunday (around 6 pm) was almost at capacity levels--I think this is due to its "hub" status.
Also it's basically the only AA/US "megahub" with a Centurion lounge, and there are people who claim they preferentially route through there because of it. (Yes, LGA has one, but it's not as easily accessible to connecting pax.)
Anyway, perhaps the MIA location will help this congestion some.