Hand caning puts the recipient facing the caner and the cane can be clearly seen, the trauma is different but no less daunting or humiliating than being caned on the bottom I suspect.
Although it was perhaps more to do with the nature of the teacher rather than the methods below, I would submit:-
Girls having more delicate hands would feel the pain more on the hand. Punishment on the bottom could result in protruding girly bits being struck and fatter bottom absorbing sting more. Also as girls get older bottom punishment can stimulate after the initial painfull effect.
Boys caned on hands when young because hands not unlike a girl. Bottom a bit fatter thus absorbing strokes better?
As boys get older their hands toughen up, as the bottom becomes more muscular then it may sting more there.
If you get the drift.