Well.. silverwmoon's thread inspired me to ask this question that I heard a lot.
If you had to take a life of someone else... which would you do? Which guilt would you rather endure?
(1) Press a button. You are flying an airplane and by pressing this button you drop a bomb on a city and kill a thousand. You are responsible for the death of a thousand innocents. However, you never actually get to see your victims suffer and it is a fast death.
(2) Stab one person with a knife. It's a painful way to go, yet you only kill one person and spare many others. This takes more psychological strength to do since you probably would remember your victim's faces and screams for a while.