I would build the Yukon for the main reason you mentioned it's paid for and you won't feel as bad when you scratch or dent it. Getting parts is another, most towns if they have only a couple of dealerships they will probably be Chevy, Ford or Dodge. Every parts store carries parts for GM trucks. In the Yukon most of your gear will be secure inside, where in the Titan your gear would be in the bed. If you don't like tent camping you can always sleep inside the Yukon, I sleep in the back of my Suburban all the time because I hate sleeping on the ground. I think there is a transfer case swap you can do to get rid of the autotrack, but don't quote me on that.
I never thought I would like my Suburban as much as I do, but it's the best 4k I ever spent. My Suburban being a 1999 and cheap I'm not afraid to modify it to suit my needs either. I do worry about breaking down, but I have AAA to get me to the nearest repair facility. I have also started fixing known issues before they become an issue for me. I wish I had more power, but I expect to have to replace the engine by 250k (I'm at 170k now) and when I do I plan to put the GM crate 383. It's a direct swap with only a mild tune on the ECU needed.
Good luck