McCombs for the following reasons:
1) The amount of time you must wait for a decision after you interview is at least 12 weeks, but often even longer. This was by far the longest wait of any school I applied to, and it makes me wonder what they are doing over there.
2) I left several voicemails with the office of admissions with questions, and my calls were never returned.
3) You must mail your official transcript to a separate office at UT before your application can be considered complete. This is confusing and should be made clearer from the beginning.
In general, I just felt like their office of admissions is either incredibly swamped or extremely disorganized. I know the school itself has an excellent reputation, but I was really turned off by their admissions process from start to finish.
The problem with McCombs, and someone correct me if I'm wrong, is that everything still has to go through one-single University of Texas system. In other words, any other school that is part of the UT system is using the system. Therefore, McCombs has to take an application and it has to be processed with the system as well. I believe there has to coordination between McCombs and the UT system with regards to getting payments, transcripts, etc. Obviously, if McCombs were to handle everything directly then I'm sure things would be easier. To your second point, not all schools return calls right away or at all (this from experience). Back to your first point, 12 week is a lot but I've had to wait 10 weeks for some decisions. Now, in order of ease, yes, McCombs is probably the more annoying one but hey, I blame the system I guess. Yale is by far the easiest as far as actually submitting an application.