Having owned a fully loaded 1/2t GMT900 'burb...I would steer you away at this point from that generation. The 6 speed hunts (they come with 3.08 gears), mind you, mine was tuned and had the exhaust opened up...fully loaded with kids, gear, and dog, it would only do about 14.4mpg @ interstate speeds. That's real world hand calculated numbers. I will NEVER own another 1/2t Suburban (GMT400-present, solid axle rigs are different). I did own a 2500HD CCSB pickup with the 6.0L/6L90E, and it towed everything I ever wanted, but I still didn't love the interior. I think it eeked out a 15.1mpg trip one time at 68mph with a tail wind. The 6.0's need RPM to do the work, they don't have the low end grunt most are used to with SBC/BBC platforms. So be prepared to tach them out when you need to get to the useable power.
I voted GMT800 with the 8.1. A local mechanic had one that was tuned, and other than the stated oil consumption, it got similar mileage to my K2500 454 rig...with more power.
After the GMT400 rigs, the second and 3rd row room was squeezed down a bit...I would ride in the 2nd row of mine, but not the 3rd. For a vehicle that is not used everyday, and needs to be a Swiss Army Knife Jack of all Trades....go with the big block K2500 rig. Be picky, and find the cleanest, lowest mileage one you can for the money.