I used Rivendell Ruffy Tuffy 27c tires for years and loved them. I wasn't so wild about them off road. I currently am using Panaracer Pasela TG folders in what they call a 32c. It's really more like 30c, IMHO.
Picking a tire is choosing a set of compromises. Better off road means losing a bit back on the road. Heavy usually means reliable, durable. But, of course, it's going to be slower.
Some brands seem to be slower than others, especially when the tires get bigger. The Marathon Racers I used are smaller than my Paselas, but heavier and a fair bit slower.
I'd suggest trying what I am using.
http://www.nashbar.com/profile.cfm?sku=4286