The F250 and F350 are virtually the same truck. If you are going strictly by the door weight sticker, go with the F350 with 18" wheels and camper package. If you are going by the components used, get either a F250 or F350 with 18" wheels and camper package that best matches what you want for the price.
Unless you plan to tow behind your truck camper, go with the lighter gasoline powered engine to increase your overall payload (if you are a door sticker guy). Rear axle loading capacity will change little between the two engines.
