Most trails in this country can be run with 35's, so the 40's on the Prospector XL aren't necessary. That said, I understand the desire for the AEV trucks, I send an email usually every other month to AEV nagging them about getting into the Superduty market lol. I am currently on my third F-250 King Ranch since 2012, my current truck is a 2017 F-250 King Ranch "Alumiduty". I absolutely love these trucks, loaded to the hilt with options and creature comforts, and they can tow pretty much anything you throw at them. In regards to the 6.7L Powerstroke, they have all been flawless in regards to reliability and they have never let me down in the capability department. I truly believe that Ford makes the best all-around heavy duty truck on the market. That said, I would certainly consider a Ram if I wanted a manual transmission and a Cummins diesel, but the rear coils on the 3/4 ton is a turn off.
My truck stickered for $75K, I paid $63,980, so the deep discounts on these trucks are certainly there, don't overpay.
My plans for my truck are either a 2-2.5" level or 4" lift with 37's, probably a camper with a RTT and some bumpers/winch. These trucks fit 37's with a leveling kit and honestly that's more tire than anyone will ever need off-road in an overlanding environment. Sure the cool factor of the 40's on the Prospector is appealing, but the added weight just leads to more wear and tear on the front of the truck and the tranny, two areas that Ram's are notorious for having issues. I would think that you'd want a tune running that big of a tire as well to make up for the lost power and torque, a risk if you are still under warranty.
In regards to resale, I sold my 2016 with 33K miles on it in May, I got $51K for it, I only paid $60K for it 17 months earlier, that's pretty good resale and low depreciation. These loaded out models like the KR and Platinum have excellent resale on the used market. The massaging seats sure are nice on a long road trip too, my other half hated the idea of them when we first got the truck, but now she's constantly using them lol. I would think that you'd have a much easier time selling the Ford as well, the Prospector XL definitely has an appeal on the used market, but it's only appealing to a very small, niche portion of the market and that would lead me to believe that it could take longer to sell. You certainly wouldn't want to take the hit on trading it in as I'm certain most dealers would value it as a normal/standard Ram truck.
At the end of the day, I don't think that you can go wrong either way, but personal bias aside, I think you would be better off with the KR and a small lift/level. Don't rule out the Lariat Ultimate package either, you can get all of the same options as the KR and Platinums for a few thousand less, possibly putting you sub $60K on the purchase. That would leave you quite a bit of scratch left over for mods and accessories. Keep us updated on which way you go, I would love to have another full size build thread to follow.