I've had several diesels and now a big block Yukon XL. The diesels had slightly more power than my current big block, but not by much. What the diesels had was increased MPG. BUT when you factor in the increased cost of diesel fuel AND the increased maintenance cost, it came really close to a wash for me. Any part that has to be replaced on a diesel seems twice what a similar part would be on a gasser. I think the total cost per mile (including maintenance and fuel) is less on a big block.
As has already been stated, little things and people add weight quickly. I rolled my rig across the scales one time. After adding camping gear, people and fuel my suburban weighed in at a little over 8klbs. I think complete empty weight is around 6,500lbs. That's why in mine (and many people's) opinion it's best to start from a 3/4 ton platform. When I switched from a pickup to the Yukon XL, I couldn't be happier. If I was going to really want to be nimble I'd get an add on tent like this one
HERE There's probably better ones out there, I just found this with a quick Google in order to show you what I was thinking. This way you can sleep in the suburban / yukon and use the tent space for dressing, cooking, lounging etc.
Just my 2 cents. But honestly I think expoing (in my very, very limited experience) can be done many different vehicles. It's all about which comforts you want, and how much you want to modify. But I've been able to take vehicles in places I was really surprised that were not heavily modified for offroad use. So I would focus on vehicles that fit your family and comfort needs well before you choose one with offroad prowess.