I wouldn't say i've seen anything to indicate which sex is a more brutal tickler, as I think there are brutal ticklers who are male and female. I will say though, there does seem to be a certain...pleasure I tend to see on the faces of female ticklers that I don't see as much on men. Perhaps because of the change in power dynamics? Generally speaking, I think on average, the average guy can/could physically overpower a woman and tickle them, and while most women can't. Because of this, I can see a woman enjoying being able to tickle a bound male in a way a male couldn't enjoy tickling a bound female, if that makes any sense.
Just my thoughts.