I had been wondering the difference between gravel and CX too, as around here, I haven't really had a need for either. Gravel routes aren't exciting and there are enough cars that there is no safety benefit. Plus, I hate eating their dust. We grew up riding on gravel as the only paved street in town was US85. Country roads were fun to ride up until that big farm pickup or grain truck blasted by and we choked on the dust, sometimes from the ditch where we had to bail out.
But, given different terrain like everyone's picturing here, I'd be all in!