Our cocker was a boy and he loved my mum best to the extent that he wouldn't go on a walk with other people (e.g my dad). Tilly loves everyone! She sometimes barks at men, but never at women.
I think it's all down to how they were brought up though, my mum totally babied our cocker, where I've tried to make Tilly friendly with everyone and not overly dependent on me.
Like Jojo, I think the nature of a dog and how loving/sociable they are is down to their individual personality, not gender. its impossible to generalise and say "he is a boy so he will be more loving" or "she is a girl so she will like everyone", just like us humans!
A happy, healthy well socialised pup is far more important than what 'bits' it has!