Hey Marg, welcome to the forum. You can probably tow a 21-24 foot 5'er safely with either pickup. I wouldn't try to go any bigger. Check the tow ratings of both pickups and then look around at the RV dealers to find what smaller 5th wheel trailers will fall in the tow weight ratings of the pickups. Remember the weight the RV dealers will emphasize will be the dry weight of the RV. The weight of the 5'er will go up significantly when you load the trailer.