Hey Laith,
I'd also suggest the Navara, with the knowledge that their underbody clearance isn't great. Purely based off feedback from my father-in-law. He's recently put in an order for his new work truck - and went with a dual cab Navara with custom back.
He's been driving a Ranger for the last 2 yrs, and while he says it's a great truck (lots of power), he much prefered the Navara he test-drove. The fact that it's a bigger cab goes over well with his crew - 4 big blokes packed into the Ranger, and it's a tight squeeze. The Navara seems to be wider, resulting in much more shoulder room for everyone. He also commented on the Nav being noticably quicker in the test drive.
He discounted the Triton very early on - they've got a few of them as work trucks, and apparently the feedback from their crews has been almost universally bad. Everyone complained about the turning circle, compared to the Rangers and Navs. Now, I'm sure that:
A) they're a great car (I'd actually like one myself, to be honest), and
B) the turning circle isn't really that bad,
but it seems that everyone that drove the Tritons back to back with the Navs or the Rangers came away preferring either of the other cars. Keep in mind, a lot of their work is tight, close driving around things in unmaintained locations to find inspection points, etc, that aren't always well marked. So a highly maneuverable vehicle is always going to win for them above pretty much every other criteria.
From memory, with the Ranger and the BT50 pair - one had relocated the intercooler down very low behind the bumper, and their was concern that it was vulnerable to damage that would stop the car in it's tracks. The other had the intercooler mounted much higher up and better protected. I can't remmeber which one was which though. If you're concerned about "battle damage", it might be worth looking into. I believe it's an easy fix to retro-fit the other car's intercooler and plumbing, but probably not something you want to bother with on a vehicle that's not yours.
On the DMax note, my Dad's got a Colorado (single cab, 2WD), and it's a great car.
Long story short, I'd be happy with any of them if they were given to me, but if given the choice I'd be ticking the Navara box.
Good luck!
Matto