Do yourself a favor and go to Fords 'build it' site and price out an equally trimmed F150 HD and an F250 gasser. You'll find that the F250 will be the same price or too close to it make any difference. The F250 will come standard with some of the things you have to add as options on the F150. You'll also pick up around 3000lbs of payload by going F250. Both trucks are almost identical in size. Both trucks mirrors are going to stick out the same.
Go to Fuelly.com and look at mpg's. EB F150's with the 3.73 don't do all that well. You have to have a light foot to get the mpg ratings.
With the F150 HD when you reach the trucks GVW you're at the RAWR. Not so with the F250. RAWR and FAWR are normally higher than the GVW.
Read around and you'll find that 99% of guys towing with 1/2 tons are at the max for all load ratings. Also you're limited to the size of the 5th buy going 1/2 ton. Once you have the payload capacity you have the ability to move up to a bigger 5er. Bigger isn't always more money either. You'll have a chance to get a bigger 5er that may be discounted and be close to the same price of the smaller "1/2 ton towable" unit.
