Flat towing question regarding E450 chassis

[Flarider]

I have a Leprechaun 260DS on the Ford E450 chassis. Been flat towing a 2013 Honda CRV for the last three years. It works great for this purpose. Weight about 3200 lbs. and really the only time I feel it behind me is in the mountains. I need more room and a pick up bed. Have been considering a Chevy Colorado or a Ford Ranger. Specs on both of these vehicles are very similar with each being about 800 lbs more than the CRV. I am wondering among those that pull either of these vehicles with a similar class c E450 what your impressions are. Very interested in your opinions particularly mountain towing with a 4000 lb vehicle instead of my CRV.