Right, lets get this straight once and for all:
A rabbit in a stop end will sit tight regardless of whether it can get past the ferret or not so size and gender have NOTHING to so with it.
Jills tend to be much faster than hobs and are also quicker, so are actually more likely to get over the back of a rabbit to kill.
Some ferrets are better at killing than others. My hobs never kill, the jill we work has a real knack for it.
I'd suggest people comment using knowledge and experience, rather than recycled opinions they've read on the Internet.