Until Serena came along, May was my favorite, I loved the whole of the AG anime. Wasn't too into Dawn's character, I found her a little annoying. Just personal preference. I think in terms of development they were close to the same, and both changed quite a bit. Dawn isn't a bad character, I just much prefer May. I liked her personality, and the fact that she started out mostly disliking Pokemon, but ended up with her dream being tied to Pokemon and Contests.