I am against slow, painful, torturous deaths. Simply because, if they deserve to die (and I'm not touching the subject of who gets to decide that and if its right or not), then they need to die fast and be certain of the outcome. The longer you take to kill them the more time you give them to wriggle out of it.
Osama? Bullet to the head, take a picture, bury him and forget him. Best thing you can do.
Saddam? Same thing.
You put either one of them in prison, anywhere, you only prolong the chance that someone can "rescue" them. Nightmare starts all over again.
Every second you let a true monster stay alive, no matter how good security is, you increase the chance he can say or do something to hurt someone else before he is gone. Get it over with and move on.