It never ceases to amaze me how many folks always chime-in whenever a buyer is looking at a V6 to rationalize why they're happy with a V8 and why everyone should get a V8. It's silly.
It's a matter of personal preference and best left at that, since each engine & accompanying drivetrain has well-documented opinions that are readily available to said prospective buyer. Both are great engines and drivetrains, each has its Achilles' heel there isn't one clear winner.
For a little more power, sure, go for the V8. But the tradeoff will be crappier mileage. How much crappier (or how much better the V6 gets) depends almost entirely on driving style. A leadfoot might as well get the V8 because trying to jackrabbit a V6 will probably make it get substantially worse mileage than the V8 under those demands. A hypermiler in a V6, though, can make the V8 look like a gas hog by comparison. The right choice? The one that fits one's driving style.
Anyway...
I'd be primarily worried about the rust on a truck with over 100k miles. Corrosion just makes every little job an ordeal, and that's getting to the mileage where more and more things are going to need to be replaced.
I'd look closely at the frame for signs of rust (the deep rot, not superficial surface rust), and inside it for signs of sand & dirt accumulation. Also see if the skid plates are all bashed-up. If the truck only left the pavement once in a while, it's not going to be as much of a headache as if it was crashed and thrashed around offroad or driven over rough gravel roads on a daily basis, in which case it might need a whole lot of corrective work, including work on steering, alignment, bushings, ball joints, etc..
XREAS is more things to go wrong, but sounds like it's really nice when it is working correctly. I'd bet it would be really obvious if it was failing, the truck would probably handle like utter crap.
The price point doesn't seem too bad to me, assuming it's in as good of condition as it sounds. Dealer or private party? If a dealer, I'd go over everything super carefully, they buy from auctions and won't 'fess-up even if they know a trade had needed a lot of cleaning-up to make it look as if it hadn't been run into the ground. At least a private party might be able to give you an honest assessment of how they'd driven and cared for it, and may talk too much to make sure they don't have a guilty conscience over selling to you.