In stock form, the best offroader pickups are the hilux, ranger and bt-50. Yes the navara is big, wide and sits lower than the others, so you either need to change yojr driving style offroad or modify yojr navara like I have. However, my own navara hasn't been too bad off-road.
Just to clarify, when I say stock form, I mean the only upgrade is a good set of all-terrain tyres like bfg at, terra tracs, or kumho kl78. Otherwise, once you start modifying and upgrading suspensions, mud terrain tyres, diff lockers, winches, etc - they pretty much equal all round.
I chose the navara over the hilux cuz of my budget at the time... The navara was more affordable both in 4x2 and 4x4 trim over the rest of them, even the ranger and bt50 - and I was looking for a manual 4x4 with fabric seats. Plus it was the second most comfortable (after the hilux) and most powerful at the time (new ranger is now more powerful but is 1.5x the price).... Back then I figured I could modify my navara to be an offroad monster and still cost less than a stock automatic hilux (and I was correct!!).
When it comes to maintenance, a 4x4 would have slightly more maintenance to do cuz the front diff will need stuff like fluid changes, the 4wd system needs periodic attention amd maintenance, etc.
I do most of my own maintenance now, with a little help every now and then from a mechanic friend.
Otherwise, a diesel truck is a diesel truck...... Regular maintenance is required to keep your truck happy and working well.
Best advice I can give u is to test drive all the models you interested in.... Put in the hours and research. That way u can make a decision that's best suited to your needs. I took 6 months to buy mine and I have no regrets at all!!