We have the 2100 with the 350 and do not tow so I can't advise you. Go to the PC website and forum members will give you great advice or call PC direct for info.
The E-450 has a lower axle ratio which will help with towing a heavy load. It also has stiffer rear springs which will be more harsh than an E-350. I went for the E-450 because I'm a frequent mountain traveler. If you're a flat lander, maybe you'll be happier with an E-350.
I have a E450 Phoenix Cruiser and tow an enclosed trailer with our Wrangler inside. No problem at all with the V10. I prefer having the more heavy duty parts the 450 Super Duty uses. Gas Mileage will be worse with the 450 obviously but then again it's never great for a MH anyway.