Blue signifies the states I think Obama was the better fit; red for Hillary. It's truly a shame these two were never paired on the same ticket together. Their unique regional strengths would have been interesting to see fused together in a general election.
All in all, it's difficult to precisely state who would do better against McCain. My hunch is Hillary does a little bit better in the electoral vote because she had the potential of flipping quite a few of her husband's states in the South all while keeping most of Obama's states.
Flipping IN was all Obama's doing (Hillary couldn't conceivably have flipped it without Bayh on the ticket), NC is a toss-up/tilt Obama owing to record black turnout & VA was flipping this year regardless although Hillary would've taken the traditional Democratic route via SWVA to win it. That county map would have looked very, very interesting... But Obama would have probably done marginally better than her due to his strengths in NOVA and the Greater Richmond area, all despite carrying significantly fewer counties than her.
WV, MO, AR would have almost certainly flipped to Hillary and she may have even come close or even won GA, KY, LA & TN (in that order). Therefore, it seems Hillary had the electoral edge over Obama. A bigger popular vote margin than Obama's +7.3% also isn't out of the question if Hillary can muster a final hurrah of white ancestral Democrats in the presidential level. I think after 8 years of Bush, a Nader resurgence is also unlikely.
And ultimately, as I hate to admit, a Hillary presidency would have been better for local Democrats in the more socially conservative parts of the country. Not to mention Cocaine Mitch would have been fighting for his political life with Hillary targeting KY with all hands on deck in 2008. I just don't see anywhere near as mass of an exodus in Appalachia happening under a second Clinton presidency until at least a second (inevitable) Obama run in 2016, which is when the bottom would really have fallen out.
