McCain's advantages:
1) experience both in the armed forces and in the Senate - these are both immense assets in the next point.
2) foreign policy - Obama has shown a naivete on foreign policy. He's had to back off earlier claims because while on the surface they may sound appealing, they fail to recognize the immense complexities of foreign diplomacy.
3) related to the above, McCain views terrorism and other global threats as foreign policy problems while Obama is moving towards the law enforcement model favored by Clinton and Albright.
4) tax policy - McCain's isn't the greatest but it should be more neutral on economic growth than Obama's which intentionally or not attacks businesses via straight taxation and increasing the cost of capital.
5) economic policy - McCain's is definitely more pro-growth.
6) spending - McCain has a solid track record of attacking wasteful government spending. Obama's camp proposes a new entitlement each week it seems.
7) cooperation - McCain has a proven track record of working across the aisle to get things done. Obama has very little such expericence and in numerous chances for cooperation, he has chosen party line.
8) intangibles - Obama is an unknown; McCain is a known
9) power balance - The congress is likely to be strongly democratic. McCain will provide a power check to a full democratic agenda. Obama will enable a full democratic agenda.
10) Energy independence - McCain favors an all options on the table approach. Obama rules out more oil exploration and wants to punish oil companies - this will not move us forward.
11) Global warming and health care - McCain's approaches here are more measured and work more within the existing system. Obama's approaches are more drastic but unproven.