Sorry I waited so long to respond but I first got distracted and then just forgot.
I think that how we interpret the term Ego is where our disconnect is. My perception of Ego differentiates from yours, in this respect, so that would obviously hinder our ability to communicate our perceptions in this case.
Now you agree with Clay's assessment that girls tend to mature faster than boys and I am also on board with that. The level of maturity in boys is the crux of my perspective of the role that ego plays in this case. While the definition of the term ego might have both a positive and negative connotation, I tend to believe it to generally to be negative, but for this argument it makes sense to keep it simple so I won't go into much depth to explain my reasons. So lets stick to your statement of Ego also being interpreted as confidence as our operating parameter.
The term ego is usually defined as a persons self image. So yes Ego could be interpreted as a source from which a form of confidence originates. The key is whether it is confidence based on reality or illusion ( in this case usually an agenda driven rationalization) . This is where Clays statement about maturity comes into play and also the crux of how society creates different pressures for boys and girls. That is why I stated that a boys identities were more closely related to athletics and thus a creating more pressure for proving their worth though that medium. It does seem that the present emphasis on womens athletics is tweeking that dynamic to some degree.
A persons true sense of self requires objectivity and visa versa.
Our society tends to delay the maturation process of our young people. In respect to boys there are very few avenues to do so. In so called primitive societies, they had a ritual that once boys passed they were considered men and accepted into society as such. Our society has no such defining rituals. Guys spend a ridiculous amount of time trying to prove themselves mostly using self defined standards based on their own immature perspectives. Athletics was one form that society provided as proof of manhood. That is why boys are more likely invested in athletics in the formulation of their identities as men.
Girls are socially free'er to express emotions than guys, while guys are conditioned to not show them. This would tend to mask what is comparatively happening internally in respect to what they express outwardly. Guys tend to use repressed emotions as a " waterboy" type competitive motivation ( tackling fuel ). Now this might partially explain why guys tend to be more competitive in athletics than girls. It provides an emotional release for them. Now we also see that competitive fire in many girls but to a lesser degree. But egress into the area's that are more important to women and you will see some real competitive fire.