I was such a tomboy growing up and, of course, my two best friends in the neighborhood were boys. We would play dress up and pretend we were superheroes and I, inevitably, was Wonder Woman. What lessons did I learn from her? Well, that she could be sexy, powerful and still kick ass and I am not so sure that's what I want my son to learn about power and kicking ass (it isn't always sexy).
Perhaps if I had a young daughter, this answer might be more clear to me as far as which superhero I would like to be and why, but for now, I'm happy with the idea that there are more options for young girls to choose from and more realistic characters for them to relate to and aspire to become as they get older.
And yes, I do hope that my son (and all young boys and girls) grow up to be powerful, sexy and still kick ass (just perhaps not all in the same day).