Really? Well, the argument is presented here:
'Women pilots are best for modern airlines' - Learmount
Apparently they are better at teamwork which, in the latest generation aircraft, is what it's all about (assuming basic aptitudes, of course).
I think it's dangerous to generalise. I've worked with good pilots and indifferent ones, and the pilot's sex doesn't seem to have much to do with it. But why are there so few women who want to do the job?