When we were combine shopping 8-9 years ago we looked at several combines locally before we went to a dealer liquidation sale up in ND that had a whole pile of Canadian combines on it.      All of those combines out of Canada were setup for small grains.     

All of those small grain combines had significantly less wear/hour than the combines that I had looked at in this area.   This area is 99.99% corn and soybeans.

Soybeans are abrasive and you run dirt through the combines.    Corn isn't nearly as abrasive but you run massive bushels through the combine.

Wheat/oats are neither abrasive or massive bushels.