Both are incredibly good schools, and you'd be fine at whichever one you choose. That said, the things you might consider are commute (do you live in the OC or LA?) and apartments in the area. I am an international student, i'll either be taking on-campus housing (if available ) or off campus housing for both schools
Also, would you prefer to finish your degree earlier since you start in fall at UCI vs the next spring at USC? I have been informed that UCI has 10 week quaters and the degree automatically ends in 1.5 years rather than 2 years ( even for MS without thesis option) However i am interested in Computer vision and USC has a computer visiona nd image processing track, whereas UCI has comparatively limited options.
Also, what is the deal with your funding; is your work paying for it or did they offer fellowships? I have not been offered any funding or scholarship at either school
In addition to the above queries i'd also want to know if job prospects in engineering field are effected by the ranking of these two schools? @seizing