The only real difference I've noticed, is that you take significantly more damage on Warrior than you do on easy (or whatever it's called in this game.) Enemies seem to take the same amount of damage on all difficulties, and ammo/money/items are just as common.
the real answer is a mild increase in damage to you and a mild decrease in your damage to them. but by the time you know the ins and outs of the game they really do change nothing. basically QTE sequences are more unforgiving/frustrating - that's the only thing that really changes.
After a while of playing on hard (warrior), the main thing that bugs me is that small falls hurt so much, when i played normal i used to slide down mountains no problem, but now i have to take the slow way around