Statistically, the Best Director award goes to the same film that gets Best Picture about 85% of the time and is usually a good indicator for choosing a winner. Looking at the last ten years, though, that statistic drops to about 50%, making this method a crap shoot. Complicating things slightly, the five Best Director nominees line up perfectly with the Best Picture contenders this year, meaning that no one can be easily eliminated.
The next step to choosing a Best Director is to look at the total number of nominations for each film. David Fincher's Benjamin Button leads with 13 (two of which are for acting, which bodes well), followed by Danny Boyle's Slumdog Millionaire with 10. This makes these two movies the major contenders for Best Picture and, therefore, Best Director.
I'm going to give my pick to Danny Boyle for Slumdog Millionaire. While Benjamin Button was more classically pristine and will do well in the artistic and technical categories, Slumdog showed off Boyle's uniquely kinetic style. Danny Boyle for the win.