I started reading the posts, then got a head ache, so as an excursion owner with a TT near your same length, I will give you some advice.
1. Don't buy a gas truck no matter what it is, chevy, ford or dodge.
2. I have owned, both suburban's and Excursions, the ford is WAY WAY bigger inside and WAY more comfortable for my family with four teens.
3. The excursion diesel pulls like a dream, and the 05 models have engine braking just by tapping the brake pedal.
HOWEVER, the downside to the excursion is the fact the wheel base is shorter than that of a pickup. So a long trailer tends to push the excursion around a little. But when we switched to the diesel that issue went away and it pulled much better.
If you don't need fourwheel drive, I would take and heed what others are saying, a 1 ton diesel van would be a perfect cross country road trip vehicle.
In either chevy or ford.
NEXT, STAY AWAY FROM 2000-2002 Excursions in both 7.3 and V10's . The 7.3 have weak transmissions, the V10's have head issues.
As for Ford V10's, I would not buy one to tow with unless it had 4.10 or 4.30 gears. These engines have a very bad flat spot in the RPM range due to the overhead cam design. They don't like to tow a heavy trailer up a steep grade.
Since having a diesel and towing with a diesel, I will never go back to gas.
As for fuel,
V10 was 11-12 around town empty and upto 17 on the freeway
v10 towing the trailer in my sig, which is 39' tail to tongue, was 8-9mpg with premium.
6.0L was 14-15 around town empty and upto 22 on the freeway
Towing same trailer 10-11 mpg.
As you can see the city and freeway empty pays off, but towing is not much more in MPG. But the difference in towing ability on the excursion diesel was instant. I would not ever buy a gas engine again. The diesel just pulls and pulls.
In closing, I would also suggest you not take peoples words or the internet for what a vehicles actual rating is. Both GM and Ford offer Fleet guides or up fitter guides that will show true ratings. Nine times out of ten the info at all the car sites are incorrect.
As an example, the diesel excursion is a GCWR of 20,000# with a Trailer MAX weight of 11,000# towing. BUT IT IS NOTED, as the military used the excursions, that rating IS BECAUSE the truck is built with the hitch BOLTED on from the FACTORY as part of the "Blocker Beam". The 11K rating is based on the fact that the HITCH is only rated at 12k. If you changed the hitch, you can tow a heavier trailer, but must monitor the GCVWR.
You should also know, that unlike GM, Ford has no mention of Weight Distribution hitches, which changes the tongue weight of the trailer.
If you are too look at the ratings for any 05 ford F250, F350 the bumper pull trailer max is 12,500 lbs, but the fifth wheel is 16,100#.
The excursion shares the entire drive train from the pickup, and only differs in springs. But the pickup springs can be put on the excursion to increase load capacity. Just like airbags and such.