The answer depends on your desires and mileage.  I have a 2001 Chevy 8.1 Gas engine.  All the truck does is haul the trailer and trips to the lumber yard.  After nine years, it has yet to break 28,000 miles.  I've been pleased with the fuel & maintenance costs compared to a diesel.  I do have to fuel more often and drive the engine to higher rpm than than with a diesel.  I don't have to suffer the diesel noise and I still have the $4000 difference from the initial purchase.

This year, I'll do a month of traveling... about 3000 miles in one trip. 

The one performance area that a turbodiesel will be better than a gasoline engine is high altitudes.  5000 feet or better ...  If you were to do much Rocky Mountain driving then the turbo will produce more power for towing at altitude.

If you are purchasing a diesel, because you are concerned about the mileage of the gas motors, you will be disappointed. It will take a few hundred thousand miles of driving, to recoup the additional cost of the diesel motor and its additional higher maintenance costs, over the operational expenses of the V-10.

The V-10 is a good motor, with many satisfied owners. It is a good motor to use if your driving is combined, with trips and running about, with often starting and stopping. It will haul heavy loads across many miles, and pull the hills, albeit at some higher RPMs.

If you travel mountainous terrains, pull very heavy loads and like to cruise at high speeds, the diesels will do all that well. For that power, you will spend a considerable amount of money over the V-10 option. Both engines will tow well. What you need and what you want, will determine whether you choose the diesel or not.

Gard

If you think you really want the V10 then you best get one now!! 2010 is the last year for a Ford V10 in a 250/350 pickup... They will continue to offer them in the 450/550 cab and chassis. A 6.2 liter V8 gas will be offered in the 2011 250/350 pickups. This V8 will be up on horsepower but down on torque from the V10. The V10 being the more powerful of the two gas engines.

A F-250 with the V10 and 5 speed automatic would handle that trailer well.

I have a 2008 F350 6.4 liter Diesel.  I get as high as 14mpg empty going less than 65 mph.  I get between 9.5-12 mpg hauling a trailer depending on speed and terrain.  If you bypass the emissions, you can get a lot better, but it is illegal.  Those are my findings with his truck after 2 years and 30k miles.  Newer trucks, or even other trucks may vary. 

I also have a Chevy 2009 2500 HD 6.0 gasser that gets almost the same exact mileage after 10K miles.  It has less power but is adequate to pull smaller living quarters.  Nice 6 speed transmition that you can easily manually put in any gear desired.  Works great going down hills.

My personal opinion is the 6.0 gas engine is nice for smaller trailers, less maintance and a lot less money upfront for the truck, easier winter usage.  I know this is not the same size gas engine as the Ford.  If you haul a large trailer down the interstate and up moutains often, the diesel doesn't work as hard to keep consistant speed.

My 2 cents.