Here's my opinions on full-size SUV from my recent vehicle courting spree, ranked how I'd buy them---
1-Turbo diesel Excursion (awesome tow rig/family truckster--drawbacks price)--cheapest I've seen was around $18k for a 2000 model on e-bay--roughly 15-18 mpg--heavy towing about 10-12ish
**---V10 is pretty cheap (down around $12k-18k) for some decent trucks with 70kish miles. There's lots of high mile V10 engines out there, but I'm a little nervous about them. I've not heard anything terrible (aside from some spark plug-head issues in '99-01 models), but would feel better with the 460
roughly 12-15 mpg--heavy towing about 8-10ish
2-8.1L Suburban/Yukon XL (solid tow rig/family truckster--drawbacks, fuel consumption and I don't care for the IFS 'feel') roughly 12-15 mpg--heavy towing about 10-12ish
3-6.0L Suburban/Yukon XL (solid tow rig/family truckster--better fuel economy than the 8.1L and still adequete power--drawbacks, fuel consumption and I don't care for the IFS 'feel') roughly 15-18 mpg--heavy towing about 10-12ish
4-7.4L Vortec Sub '96-'99 (solid tow rig/family truckster----drawbacks, fuel consumption and I don't care for the IFS 'feel' {newer '00 design feels better, IMHO})--VERY REASONABLY priced---$8000-13,000------ roughly 13-10 mpg--heavy towing about 8-10ish
5-7.4L TBI IFS Sub '92-95 (solid tow rig/family truckster----drawbacks, fuel consumption and I don't care for the IFS 'feel'--less power than the Vortec {newer '00 design feels better, IMHO})----can be found for CHEAP in decent shape $3500-8000-----roughly 13-10 mpg--heavy towing about 8-10ish
I don't care for the Expedition for a tow rig. They just don't seem to have enough power/grunt (5.4L) and they've got the IFS Ford thing....... If I'm going IFS, it'll be a GM. With your 22 ft. boat, I'm thinking you're wanting the diesel Excursion (that's gotta weigh 6000-7000 lbs headed to the lake). That's more than I want to tow with a 1/2 ton chassis/springs/brakes of any kind.
Off-road...... They're almost all equivilent for off-road use. They're HUGE and won't fit into spots that you might want to go, but are probably OK for their size. If you want to lift it, the solid axle Ford wins again.....(d@mn GM)...... price of lift, ease of installation and breakover angle.
That said, I have a '89 TBI 5.7L 4x4 2500 Sub that 'does the job' (climbing hills is not it's forte, but it's not bad other than that). I think we'll end up with a 7.3L Excursion in the next year or two (or if I can convince the wife, a Cummins or 7.3L crewcab pickup)