It can be seen why Jill ferrets are popular as working ferrets. Their size enables them to pass with ease through the net, and they are less likely to disturb the net. White ferrets are popular as they are more easily seen by the operator.
The bottom picture shows how a Hob ferret (Charlie) would unset the nets.
Fred explained to me how hobs are used to drive rabbits from holes to shot by guns or caught by dogs rather than captured in nets.

Entering a burrow.