I start on the easiest then play the hardest if there is a reward. I keep the difficulty on very is for fallout 3 and new vegas because it doesn't make sense for a few .308's to the head to not be able to kill anything or my pulse gun not to short circuit any robot. I'm preserving a semblance of reality but really I'm just very stingy with my ammo. Doesn't feel right to have less than 5000 rounds of each ammo type on me.