Cross rims are in general wider (and hence beefier) but many people, particularly those wacky MTB folks, run wide tires on narrow rims.
Right now I'm running a set of IRC Mythos CX (700x42) on a pair or Mavic CXP33 rims.
This is Africa, 1943. War spits out its violence overhead and the sandy graveyard swallows it up. Her name is King Nine, B-25, medium bomber, Twelfth Air Force. On a hot, still morning she took off from Tunisia to bomb the southern tip of Italy. An errant piece of flak tore a hole in a wing tank and, like a wounded bird, this is where she landed, not to return on this day, or any other day.