There's a big difference between cities and MSAs, which the parent referred to. Using city populations like that is, IMO, almost always misleading. For the given example: hit the DFW metroplex, you're hitting Arlington. Another instance of the misleading aspect of looking just at city size: Atlanta has a city population of a bit over 400k. That makes it the biggest city in Georgia, and yet isn't even a tenth of the Atlanta metropolitan area, which has about 5.4 million people.
The 10th-largest MSA is four and a half million people, the 10th-largest city is just under a million.
The 10 largest MSAs contain over 80 million people. That's already over a quarter of the country -- more than the 50 largest cities put together. Taking it out to the top 20 MSAs brings that up to almost 117 million. The top 50 MSAs cover more than half the country's population.
(And as a resident of one of the largest urban areas, I would absolutely prefer more of a popular vote. But the country is much more urbanly clustered than the "top 50 cities" stat would suggest. But IMO that's a reason for a popular vote, not against one.)
I'd argue that it's disingenuous to use MSAs rather than cities to talk about campaign stops. To use your example, the Atlanta-Sandy Springs-Marietta Metropolitan Statistical Area has four counties with more than 700,000 people, and fifteen with less than 100,000.
It's hard for me to imagine the average resident of, say, Jasper, GA (population ~2,000, median income ~$30,000) caring one way or another that you had a rally in Atlanta— but their votes still count.
Looking up TV listings for Jasper, it appears that cable carriers there still carry the Atlanta affiliates, so I'd disagree on how much they'd notice a candidate making a stop in Atlanta. In a popular vote system, I wouldn't expect any presidential candidates to stop in, say, Canton instead of (or even in addition to) Atlanta, when local media is going to pick up on stuff going on in Atlanta, so Atlanta's the closest I think Jasper would see.
That's fair, they might see it on the news if nothing more important was going on that day. But that's still press coverage, not a stop, and it's likely to backfire when the ad comes on saying, "But how much does Mr. Smith really care about Georgia?"
The more general point being that the dynamics of campaigning would be fundamentally different, such that none of the lines that are currently drawn will matter (and of course that's good thing).