Though I am not experienced, I would like to give my two cents :
It seems your aim is to get a good job (and not go for a PhD after MS).
1. CMU is ranked much higher than USC for graduate studies.
2. The very best companies will come to recruit from both USC and CMU and you will have to prove yourself no matter where you go to get in. However, from CMU they are likely to hire more students but also the competition will be tougher due to higher quality students (Google has an office in their campus). From USC, it would be easier on the competition.
Both universities have some top notch faculty (Boehm at USC is a legend in software engg.)
Remember that the major difference between the two universities would be the quality of other MS students, which would be much higher at CMU. However, that might not be an important factor for you. Further, you have to see if the difference in cost is significant between the two.
No matter what you choose, good luck with your decision !