A very common question I get asked by prospective owners is whether it is better to buy a tod (male fox) or a vixen (female fox). Before I continue, I just want to make a note that this is all second-hand information. I have never owned a vixen, so I cannot speak from personal experience on the matter.
Here is the gender debate in a nutshell: It is commonly said of foxes (particularly the smaller species) that tods make better pets than vixens and are more sociable. Another reason cited is that tods are much easier to potty-train than vixens are. However, tods are more likely to turn aggressive as they mature, have a stronger smell to them, and are more likely to hump things than vixens are.
Another common theory is that it's best to get a fox that is the opposite gender from the owner, so a man should buy a vixen, and a woman should buy a tod. This theory is based on the social structure of foxes in the wild. Foxes most commonly live in pairs (one tod, one vixen), or skulks (one tod, several related vixens). When you bring a fox into your home, your family becomes it's surrogate skulk. So a tod will view a man as an intruding tod, and a vixen will view a woman as competition in the pecking order.
This concept may have some merit to it, as Gizmo tends to be much friendlier towards women than men, but that could also be explained by the fact that my mother and I spend much more time playing with him than anyone else, so he's more used to women.
While there are a lot of opinions on this matter, remember that gender only plays a small role in your fox's personality, and other factors (such as overall health) should be much more important in making your decision about which fox is best for you. Pick a healthy, social, friendly kit first, and check out it's plumbing later.