It doesn't take much to kill a fox,if you hit it good.So, with the smaller calibers it is all about shot placement. I'd give the advantage to the .17, sinceballistically, it hasthe obviousadvanatage of providingmore accuracy at a greater range. I knocked a crow out ofthe top of an oak tree at about 220 yards with my .17. I wouldn't have even tried that shot with a .22 magnum. But then again, you could move up to a .22 Hornet and remove all doubt.