your opening a right Can o' worms here!
I do 26 front 28 rear road
18 front 20 rear off road
But your gonna get a lot of differing answers..... Why? well, I weigh 140Kg for starters, so i don't wanna go too low on pressure for fear of a 'nip' puncture.
also depends on terrain....... i don't drop the pressure quite so much if I am going on Rocky terrain as I do when its gonna be Muddy, or Sandy....
Martyn