Also on the issue of chain drive vs. gear drive, a chain drive will have a spring tensioner that will also act as a 'shock absorber' when you hit a rock or root or other immovable object, whereas a gear drive would not have this capability, other than a slip clutch, or shear pin.
As mentioned earlier,Case made chain drive tractors, also oil drilling rigs(even the largest) are chain drive. Conventional cranes are chain drive, as well as many other types of HEAVY machinery. So as far as one being superior to the other, who knows. I have repaired the cchain drive on a 84" Farm King tiller for a few dollars, where gears would probably have been expensive!!