each company looks at C and D trucks differently. For example, Panther has a .10 variance and Tri-State I believe is .05 cents. However, for a C unit, they both pay the same per mile. Currently on the D unit, Panther is 1.20 and Tri-state are 1.15 Fuel surcharge and those items would be the deciding difference. Some companies pay strictly on weight or percentage. That may or may not be to your disadvantage. If you are buying a new truck, the C will be generally cheaper, but if you compare used ones, there is not that much difference. On the auction block the D will bring maybe an extra thousand assuming they are speced reasonably close. That is comparing a class 6 to a 7. Class 8 will of course be higher. In the case of the latter, go with a D as it will have alittle more capabilities. Insurance, fuel milage , maintenence are going to be very simular. Payment and interest will be higher on a D but it should be offset by the higher rate. (.05)per mile.