My 2 cents...
I won't get into 'weights' , as it pretty much has been covered.
However, from experience towing with a F350 4x4 Dually I would add ...
..having towed a 26 ft 5th wheel, for 5 years, with this truck it was very reassuring having ample power and stability with this size of trailer.
...now with a 30rlbs Wildcat the (same) truck notices the additional weight but on the highway the truck handles it with exceptional stability and reliability in comfort...even a more stable, straight line driving, than with the smaller trailer....the added weight of the larger trailer puts the truck down to just touching the overload spring leaf....The truck sits nice and level when hitched up.
I couldn't afford a 'new' F350 so I chose to get a low mileage ,good condition, comfortable used one.
Depending on conditions and terrain...I average 13 to 18 mpg .
True diesel repairs are not cheap but (IMHO) the $45,000+ dollar difference can pay for a lot of repairs.(if need be)
Regarding the 4x4 or not... other than the obvious reasons, to have a 4x4,
The 4x4 is very useful for backing up the rig, by putting it in 4x4 low it is way better for the tranny to back up any inclines and 'super' great to back into camp site positions ...it will just idle at a slow walking speed as you concentrate on driving, but note, to do this comfortably the front wheels (4x4) should be disengaged. This can be done by disconnecting the air hoses (and plugging them) from the 4x4 on the fly switch. I can still manually engage my front wheels should which to.
Side note, I have now added a TrailAir Tri-Glide PinBox to reduce the stress on the Truck and Trailer Frame ...resulting in a more comfortable ride over all.
Good luck in your choice and Happy Camping!
'07 WildCat 30 RLBS ~ West Coast Edition ~
Trail Air - Tri Glide Pin Box
2000 F350 DRW 7.3 Diesel Lariat 89k miles
Edge programmer, 4" SS exhaust turbo/back
Vancouver Island, B.C., Canada