DPs can typically be longer and heavier while maintaining cargo capacity and tow capacity. DPS also typically have greater cargo and tow capacity.
We travel fulltime in a gas engine bounder. Because we do move a lot and prefer national and state parks, we wanted to stay under 35'. There are very limited DP options under 35' and we didn't like the floor plans of any of them.
It had nothing to do with the price and everything to do with the floor plan and size. We spend a lot more time living in it than driving it (though we put 11K miles on it in 7 months) and livability is most important to us.