This is very simplistic and only includes the "major" MSAs in each state (leaving off important areas like Dayton, Toledo, Scranton, etc., but I don't have time today), but this gives an idea of why OH is much easier for Republicans than PA. It's relatively common knowledge that a lot of suburban areas that usually vote Republican swung away from Trump, and a lot of rural areas swung toward him. With that in mind, his improvement in both states' rural areas seems to be relatively similar, but his "crater" in Ohio's major metros wasn't nearly as bad as in Philadelphia (which also has a larger percent of PA's population than any of OH's):
PENNSYLVANIA
Philadelphia Metro: 64.28% DEM, 32.58% GOP
- 1,286,823 votes for Clinton
- 652,235 votes for Trump
Pittsburgh Metro: 50.76% GOP, 45.78% DEM
- 597,389 votes for Trump
- 538,693 votes for Clinton
Both Metros Together: 57.43% DEM, 39.31% GOP
- 1,825,516 votes for Clinton (64.17% of her statewide total)
- 1,249,624 votes for Trump (42.90% of his statewide total)
OHIO
Cleveland Metro: 55.91% DEM, 40.30% GOP
- 542,735 votes for Clinton
- 391,255 votes for Trump
Columbus Metro: 49.94% DEM, 45.54% GOP
- 456,068 votes for Clinton
- 415,881 votes for Trump
Cincinnati Metro: 54.73% GOP, 40.87% DEM
- 444,043 votes for Trump
- 331,632 votes for Clinton
All Three Metros Together: 49.36% DEM, 46.42% GOP
- 1,330,435 votes for Clinton (57.42% of her statewide total)
- 1,251,179 votes for Trump (45.14% of his statewide total)
Suburban voters in Ohio are still mostly reliably Republican (even with Trump), and they are almost able to win the metropolitan vote even when counting the urban areas ... this is not the case at all in Pennsylvania. Assuming similar rural and exurban support in both states, Republicans can quite easily find a path to victory in Ohio that is much harder in Pennsylvania. This is backed up by the exit polls, too:
PENNSYLVANIA:
Urban (27%): 70% DEM, 26% GOP
Suburban (53%): 52% GOP, 44% DEM
Rural (19%): 71% GOP, 26% DEM
OHIO:
Urban (31%): 58% DEM, 38% GOP
Suburban (59%): 57% GOP, 37% DEM
Rural (9%): 69% GOP, 27% DEM
To put it frankly, suburban voters hold the keys to elections right now, and the GOP cleaned up with suburban voters in Ohio while doing just well enough with them in PA to win.
EDIT: This also illustrates just how much pundits and people on this site overrate how many *rural* voters there are and talk about this "urban-rural divide" as the defining division in our politics ... if the GOP only had strong support in rural areas, it would already be dead. They'd be relying on 9% and 17% of the electorate in those two swing states, respectively.
Those exit polls show that OH is less rural than PA, but non-rural voters in OH are massively more republican. If OH voters voted like PA ones, it would have gone 50-45 Clinton. If PA voters voted like OH voters, it would have gone 54-40 Trump.
