I'd keep the 700 x 28s. I ride mostly the road, but also do the hard packed trails. Any loose stuff is infrequent and can be handled with a secure grip and aggressive manipulation of the steering. I'd hate to give up the speed and easier going on the road and hard pack by going too much wider. That said, if you want a pretty good 38, the Specialized Nimbus Armadillo with either Mr. Tuffy liners or Specialized Airlock tubes are pretty puncture resistant. If you think you'll be in more loose stuff than not then the Specialized Hemisphere Armadillo is worth considering.
Last edited by EsoxLucius; 05-30-12 at 10:53 AM.