If anybody has ever moved from Delhi to Mumbai or vice-versa, this has definitely happened.
You are new to the city. You don't know anybody. The first question people ask (after they know your name, age and occupaion) is where you're from. In my case, when I moved to Navi Mumbai, my answer was "Delhi". I now realize I should have just said 'Iceland' or 'Kenya' or 'Cuba' and I would have met with a more favourable response.
But amidst all this, nobody takes a neutral side or admits that cities like Bangalore and Hyderabad are fast leaving both Delhi and Mumbai behind in terms of living standards, plus the fact that they don't have th ebad reputation of arrogant/ignorant people. railways accidents. molestation cases or extreme regionalism.
Let us assume for the sake of argument that both sides are correct. But what astounds me is how eager each city is to think badly about the other. For example, my friend from Navi Mumbai lives in an area whose infrastructure mimics Delhi's. Besides, Navi Mumbai is Mumbai minus the flaws, so nobody from Navi Mumbai gets to judge anyways. My friends from Navi Mumbai are privileged, they don't know what common people in Mumbai face. Also, most of my Delhi friends who hated Mumbai didn't know anything about Mumbai, so I don't know who gave them the right to talk.
Secondly, how come we don't see logic in these arguments? Logically speaking, it's impossible that people in Delhi yell and slur all the time and money is the only thing that's important and I know this because I went to a school where children of the biggest of businessmen studied with students from LIG apartments (apartments for the lower income group, with only one or two really small rooms). I never saw the latter face any discrimination. In times of sickness, our neighbours have stayed up nights for us so that the sick member of our family could be taken to the hospital. If a posh area like Sainik Farms thrives so does a 'middle-class' locality like Janakpuri.
On the other hand, nobody has ignored me in Mumbai. I see the safety risks associated with trains, I also acknowledge their position as the lifeline of commerce. If Mumbai is busy, it's also active and living life. There is nothing wrong with Mubai just because it's fast.
The fact is that Mumbaikars are programmed to hate Delhi and Delhiites are genetically obliged to hate Mumbai. I hear it's the same with LA and New York, the American counterparts od Delhi and Mumbai respectively. I now understand there's no side I can take because no side is the right one. So next times someone says Delhi is the city of dilwallas and Mumbai is the heartbeat of the nation, I'll just go ahead and say Delhi has the heart which beats in Mumbai.