If there is a hill with a 10-20 degree angle I would move.
Honestly there isn't a fixed gearing that will let you go fast on the flats without spinning out AND climb a 10 degree hill. Or am I thinking a 10% hill. Never mind.

This question has been answered ad infinitum so search for more info..
Since I was a dick in the first paragraph... go with 70 gear inches.
Here's the link...

http://www.bikeforums.net/showthread.php?t=468351