17 inch wheels vs 18 inch on tow vehicle

Thanks for your replies. Today we ended up buying a Duramax 3500. It came with the 18 inch wheels. Even though both sizes were load range E on the 3/4 ton, the 18 inch tires had about 400 pounds more load capacity. So with the tires and 1 ton truck I now have more capacity. As many of you know, when you finally pull the trigger on the camper it tends to be larger than originally planned. Even if we don't upsize we now have a greater margin of safety.