...I am on the fence whether to get a 2 or 4 wheel drive. I don't know if there are advantages or disadvantages either way.
If you are going from RV park to RV park, the reasons for having 4WD are greatly reduced.
If you are going to camp on grass, dirt, etc. at some point you will probably get stuck. Every time I parked in the grass, I knew I had one shot to get the TT moving, and if I did I was OK. Never got stuck, but I did have two close calls.
One pard I know went to great lengths to get a 3500 2WD Dodge, He said he save $6,000 by getting 2WD. He said that was a great deal since the winch he had to buy plus the 'dead man' cost that much. He tells me he has been stuck on beaches, other cowboy towns, etc.
...I'm not worried about driving in snow so much as more parts to break, more expense, if the gas mileage is different...
Its mechanical and you cannot add parts with increasing the likelihood of them breaking. All in all, if properly care for and not abused they tend to work well.
Mileage is less, but probably under 10%. Though towing capacity is reduced, most of this is due to weight of the 4WD system. For diesels, I haven't read of a difference in capacity other than the GCWR, however most diesels are 3/4 ton+ and the F150 is 1/2 ton (gasser).
To sum it up, most of my camping is on unimproved ground. With the old 1/2 ton Tacoma 2WD and my 5K# TrailManor (dually), I had difficulty frequently with two close calls over 3 years.
With the 3/4 ton GMC 2500HD Dmax w/4WD and a 9K# trailer, the first time out in 2WD mode, got stuck. Punched the 4WD button whole rig moved to hard surface with only the grass complaining.