I have more respect for the 4-legged variety than most 2 legged vermin. if I have to shoot a 2 legged one and it walks away injured, I don't worry about how long it takes to die because it deserved to get shot.
4-legged ones I like to have quick kills on and I also worry about damaging the meat. I have taken white tails at 320 yards before with my .308, but I don't shoot enough to see me confident in shooting one farther than that. I have only ever had one deer get away after being shot, but one was to many.
Also, I have never taken a range finder into the woods with me. Maybe if I did I would be more confident at those shots, but I can't even think of when I have seen a deer stand still in the rut. Most of the deer I have shot were either running or at a fast trot, and the rest were walking.