I will agree that a diesel built prior to the current Urea emissions systems holds value like CRAZY now!!!! My 2007 Duramax Silverado Classic sells for as much now as it would have in 2011 when I traded it in!!!! (even with the mileage I would have added in the meantime!) Too early to tell yet if the newer rigs will hold value the same!
As for the offroad capability off diesels, yes, a diesel with an empty bed will be VERY forward biased weight wise. That will effect its capability. That being said, there are plenty of VERY offroad capable diesel rig builds. In the case of an overland build, that initial front heavy weight distribution can be helpful as there are folks that have found themselves with almost perfect 50/50 weight distribution by the time they add their trays, campers, water supply, etc.
For the kind of wheeling I enjoy, a half ton holds no appeal to me whatsoever anymore. Older half tons were great when they were solid axle rigs and you could easily upgrade to the durability of one ton axles under them. But now, all the half tons are IFS and that makes swapping to one ton solid axles a pricey proposition! (before someone says "but wait, didn't you JUST say you had an IFS diesel rig???" yup, I did! BUT, it was my tow pig for taking my one ton solid axle equipped GMC Jimmy K5 to the trails. My Duramax only saw dirt if a parking lot happened to be muddy) So (to me) a half ton rig is a heavy full size truck body sitting on a spindly IFS frontend and a semifloater rearend. (both featuring a max of 6 lugs) I went with a softly spring 3/4 ton in the form of a 2012 Power Wagon. I get a ride that's not far from that of a half ton but with real 8 lug full floater solid axles underneath it. Also, it has an actual lever for the t-case!!! I haven't even seen a half ton recently that has a lever for the t-case. Maybe you can still get them???? None of the dealers around me ever stock them.
Of the current crop of half tons, I guess I'd pick the F-150 with a crew cab and the 5.0L. (assuming you can get a lever for the transfer case) I would say the Ram 1500 but, I am not enamored with the dial shifter for the transmission. BUT, by the time I'd think about spending the $$$ on the F-150, I'd rather just pony up some extra $$$ and get a base model crew cab shortbed 6.2L F-350 and put a Carli suspension under it for a smoother ride. (since I will admit, an HD truck (other than the Power Wagon) rides like a rock!) The styling and exterior dimensions of the F-150 vs the F-350 are dang near identical anyway (crew cab shortbed vs crew cab shortbed), other than height! Of the 3/4 and 1 ton trucks, my preference is Ram (obviously) but the Super Duty is a close second!!!
I 100% get the half ton truck as a hauling vehicle for trips to Lowe's and stuff like that (stuff that a car or SUV would be a PITA to use for- like my buddy just got his Tundra for home improvement trips)- as an on road hauling vehicle. Or, I definitely can see using a half ton full size for work for like a sign company or something like that, where you need the full size space to haul around heavy items but the don't weigh a lot. But for a vehicle that I would build for offroad (and long trips offroad with a lot of heavy gear), a half ton pickup doesn't jive for me.
The only full size half tons I've owned have been SUVs: 87 GMC Jimmy (bought mostly stock, built it with 350,sm465, 203/205 doubler, Dana 60, 14bff), 2012 Yukon (wife's old SUV, never saw dirt), 2013 Yukon XL Denali (wife's new SUV will never see dirt) I wanted to talk her into a 2500 Yukon XL but she wanted the Denali so, 1500 chassis was the required way to go.
(NOTE: yes, I realize that my Power Wagon's listed payload capacity is actually lower than that of MANY half tons but, in terms of drivetrain strength, frame strength and offroad capability, it is way ahead of any of them, as it is 3/4 ton based. (other than the Raptor but, the Raptor is built for high speed vs the Wagon is built more squarely aimed at the low speed crawling I enjoy))
Sorry to step on any toes, I'm just not a fan of half ton full sizes. Your results may vary!