The points I would usually argue this based upon are largely ideological; as you're conservative by inclination, these would be wasted upon you.

I'm generally of the opinion that most people have fairly fixed tendencies which they wouldn't wish to change, and it's a waste of time to attempt to convince all but the politically indecisive.

That, and well, I don't know enough about the specific policy points of the two parties to really comment intelligently.
I will say this, though. You live in the world's sole superpower (for the moment; keep an eye on China). Who you vote for affects all of us. And, well, I'm sure a lot of us would prefer it if you go for the one with the less hawkish foreign policy. The 'war on terror' has done little for your global reputation. You've tried aggressive military tactics for the past seven years - maybe it's time to try something else, and Obama seems to suggest he'd take a more diplomatic tack. That's my argument for, I suppose.

Still, I'm hardly expecting this to sway you.