Over all I'd say women are worse but;
Men are much worse for tailgating, charging at a junction/roundabout at 30mph hoping that the cars with the right of way will back down and let them out. things like that.
Women are just less capable but better behaved. It's fairly easy to spot a car that's been parked by a woman. Manoeuvres in general. If there is a situation on a road of parked cars making a tight spot or on a car park, a woman driver is likely to just hit the brakes and wait for you to go before she carries on. That kind of thing.
If this conversation comes up with a woman, an example I often give is this; If you were sat on a plane waiting to take off and over the tannoy came "Hi, I'm Sarah your captain today and with me is co-pilot Gemma", would you think "there's no man in there!!" most women screw their face up and say ok ok yes I would think that.