A male ferret is called a Hob and a female is a  Jill. Both sexes are equally suitable as pets.
The male can be two and a half times the size of the female.
The hob has an odour if in season, castration removes the odour and any sexual urges . Castration also allows Hobs (both castrated) to be housed together with no fear of fighting or to be housed with Jills, without resultant breeding .
A Jill ferret can be problematic if when in season and not mated, what occurs is a form of  anaemia, this can have fatal consequences.
The solutions are: (a) to mate her and raise a litter.* (b) to mate her to a Hob that has had a vasectomy, producing no litter. c) A hormone injection administered by a vet, this will need administering each year. d) Spaying, an operation performed by a vet, the ferret cannot be used for breeding  subsequently .This is a permanent solution.

* Don’t raise litters of ferrets unless you are certain you can find homes for the youngsters, there can be