I got my 2012 7.3 fx in August and have about 800 miles on it. Mostly on pavement, but I have about a hundred miles on packed limestone rail trails and a few miles on packed gravel and it does fine. Some of the paved roads I ride are pretty bad and might be worse than a good dirt or gravel road. I wouldn't want to use it on mountain bike trails or really loose gravel, but it does fine on packed limestone and good dirt roads. The stock 700cx32 Bontrager Race All-Weather Hard-Case tires seem to be a good compromise too. The specs on the CX4 look good also so probably will come down to what feels best to the OP.