I think most companies have fleet contracts, at least where I am from. I think for a lot of buyers it comes down to price point. Where I live the ram 1500 dominates the market but the deal on the Rams here equally equipped is thousands cheaper then the chev and Ford. Hitting the 2500 and 3500 series you see a lot more fords again based on price. I considered the Ford f350 dually and brand new ordered in was the cheapest truck out there. Two things changed my mind, through the research it highly suggested I needed a Ford f450 to compare to the chev and dodge 3500 the price differance evened out. Ultimately I decided based on price.