Is it better to put boots on the ground, some of whom may die and who may cause collateral casualties in executing their mission, or a (hypothetically idealized) drone that kills only the target?
Still haven't decided if I have, or there even exists, a good answer to that.
A perfect drone wouldn't do that.
But on the other hand, a perfect drone has no cost of use, other than monetary. Which seems far too low a bar to set for the seriousness of taking a life.
I suppose a better question would be, why do you feel that in this particular situation - a murderer on rampage - you still feel that it is "deeply evil" to kill them in such a way that they "have no way to see it coming", to the point where you'd prefer other people to risk lives to do it in some other way?