Auto all day long
I have have undertaken professional training for serious off road and auto is by far the best in all conditions with modern electronics, hill descent control, locking diffs etc. Having regularly driven on really rough terrain, snow, soggy tracks and wet fields I feel that you get better overall control with an auto and you never have the risk of traction loss if you need to change gear in a manual which can cause loss of momentum. Looking at trucks of these 3 my choice in order would be Navarra, L200, Toyota Hilux. I have not driven the Amorak off road, but it should be good.
I actually converted one of my Defenders to an auto! Awesome vehicle. I have also owned 6 other Defenders, Freelanders, Discovery, Range Rover etc The overall key is skill level and tyre choice which will keep you moving