I'm having trouble seeing much difference between them.

Not only are they right next to each other, they have similar population density (Ohio, with 11,353,140, is ranked 7th, while Pennsylvania, with 12,281,054, is 6th) similar geography (Pennsylvania is ranked 33rd with 46,055 square miles, and Ohio is ranked 34th with 44,825 square miles), and similar population density (Ohio is ranked 9th while PA is ranked 10th).

As to the Democratic Primary election numbers, here's Pennsylvania:

Clinton 1,237,696 (54.6%)
Obama 1,029,672 (45.4%)

Total Votes 2,267,638

State population 12,281,054 (18.46% of state total)

Clinton 1,212,362 (54.6%)
Edwards 38,305 (1.72%)
Obama 982,489 (44.00%)

Total Votes 2,233,156

State population 11,353,149 (19.67% of state total)

If the Edwards vote is added to Obama vote, the total would be 1,020,794, and if the Edwards vote is added to Clinton vote, the total would be 1,250,667. (It's tough to say where the Edwards vote went, but I suspect that most went to Obama.)

Anyway, in terms of numbers, I'm not seeing any surprises. Whatever campaign events have unfolded since March (Obama's Wright speech, Hillary's Bosnia fabulism, Obama's Bittergate) seem to have helped or damaged both candidates equally.

Issue-wise, the main difference in Ohio seemed to involve who "opposed" NAFTA the most (and who got caught lying the most about it), and who would do a better job of answering the phone at 3:00 a.m.

I don't know whether the Pennsylvania numbers indicate a lower turnout than the numbers in Ohio, but if they do, that might be a clue to voter fatigue.

Otherwise, I'm not seeing much.