Thicker tread = less flats. I'm running Specialized Flak Jacket Hemisphere in the front and a Crossroad in the rear for off pavement traction. Hard compound and thick. Not as fast as some tires but I'll trade fast for no flats. 400+ miles and no flats but plenty of things hit. Both models come in a 700 38c Might find skinnier.

Both get pretty good reviews about flats or lack there of.
http://www.ajssportinggoods.com/life...sphereBikeTire