I've just heard that I converted from the waitlist at Vanderbilt. I'm also accepted at USC with scholarship.

Beyond the cost factor (now Marshall would be quite a bit more affordable) what other things should I be looking at to make my decision? I'm very partial to Los Angeles.

Cost is the least important factor, because the value of the scholarship is smaller than the difference between a school that meets your goals and a school that does not. 
Having visited schools in both cities, I can say they are both beautiful campuses and great schools. The cities are very different but, hey, if cities were the key criteria then no-one would go to Yale, Cornell or Dartmouth. 
Vanderbilt has been rising faster than Marshall in recent years and, given the difference in costs between CA and TN, Owen MBAs perhaps have better roles. Certainly, the FT ranking shows they have faster progress, are much more likely to find work, get better value for money and have much better career services. Alumni of other MBAs are more or less equally likely to recommend Owen and Marshall. 
Take a look at: How to use LinkedIn to find the best school www.find-mba.com/board/33571

Personally, I think you would not have applied to Owen if you were totally revolted by the idea of TN. Marshall is a much larger school, with three times more degree programmes and many more students. Unlike Marshall, every MBA at Owen knows everyone else's name, and the staff:student ratio is tiny.

I was just reminding myself with Google Maps. USC Marshall is spread across five different buildings, while the Owen school is in one. 

I've just heard that I converted from the waitlist at Vanderbilt. I'm also accepted at USC with scholarship.

Beyond the cost factor (now Marshall would be quite a bit more affordable) what other things should I be looking at to make my decision? I'm very partial to Los Angeles.

Yes, I went with USC in the end.