I like the way Wonder Woman flies through the air and so forth, but otherwise, as a character, the one I like more is her alter ego, Diana Prince. What I like about Diana and Buffy is that while being strong and smart, they are also nice people.
I think sometimes when people try to write strong female characters, they overdo the strong. It's like they think that to show that a woman is strong, they have to make her icy like Kathryn Janeway and Seven of Nine, fiery like B'Elanna Torres and Kira Nerys, or haughty like Princess Leia and Hermione. They don't see how a woman can be just a nice person and still be strong. But Diana Prince and Buffy Summers show that you can be nice and still be strong.