I have travelled by both delhi and mumbai local and I can say that there are very less points to compare. AC's, Ambience, facilities, Modernisation are features of delhi metro and most important point is that all the phases of metro have been completed before time which is landmark in itself. On the other hand mumbai local are famous for its tag "lifeline of mumbai". Actually these two trains are altogether different concepts so we should not compare them one to one. BTW, it was fun to travel by local and after travelling in them I felt like a part of mumbai "aam janta" and understood that why it is called lifeline of mumbai.