Hmmm, this is really a tough choice, and there is no clear answer here. I don't think though that you should choose a school based on the efficiency of their Adcom though, but more their class profile, who hires from there, what the post MBA salaries are, how this fits your goals and industry, how the school's program fits you, the weather, and the location (here, USC wins . Now, I don't really have enough information on the specifics of your situation to really advice you, but I think that if you through all the points above, it should help you think your way through it. Also speak to as many alumni and students as you can before you make your decision. And if money is really not an issue, maybe the wise thing is to go visit the schools... you may discover things you don't realize!
Do not go to simmion! USC is much better. Simmons is just a 3rd tier school in northeast region. Hardly you can survive. USC is very famous in the west part, following only Stanford, ucb, ucla. You can easily find a job with USC but not with simmon.