Much, much, much, much, much better foreign policy wise.
Probably would have done better in Afghanistan and in fighting terrorism. One thing is certain, a lot more time would have been spent on running the country instead of giving interviews to ESPN, going on Letterman, attending basketball games, giving public service announcements, ramming healthcare down America's throat and attempting to use the disaster in the Gulf as an excuse to advance cap and trade.
Hard to say domestically, but we definetly wouldn't have spent as much money and there would be much less government involvement in the private sector.
Better on immigration forsure.
On most other issues it's impossible to tell because the President selects the members of his cabniet to handle a lot of stuff. With that said, it's hard to imagine McCain picking anyone worse than Rahm Emmanuel,Tim Geitner, Janet Napolitano, Van Jones or any of the other freakshows that have played an active role in setting policy. And as bad a choice as Palin was for VP, I highly doubt that she could do as terrible a job as Joe Biden.