The thing is, PA is filled with PCOM grads. On top of that, I believe some members of the PCOM OPTI include UPMC residencies (PCOM also has one of the biggest and broadest OPTIs in the country, especially for 1 school). Also take a look at who the DOs are that get into UPMC residencies. It's mostly PCOM and LECOM grads. Sure there's regional selectivity, but if you want to come back to Pgh, PCOM is a better bet than MUCOM.
In addition, going to PCOM, the truth is down the road you will bump into a lot of alums (networking is important and that could be a big asset), and you'll see them all over the country. It's been around for a LONG time. You aren't going to get that experience with MUCOM.
Honestly, I'm sure MUCOM will do well in the long run, but it is still untested, and as far as DO schools go, you'll have less to worry about and more going for you if you go to PCOM.