I also don't see the problem with Dawn winning. Just because she barely beat May doesn't mean Dawn is automatically the best. In fact it was so close May could have won had she used more appealing moves.
Also May barely beat Zoey and Dawn barely beat Kaito and Dawn barely beat May, Just because Dawn won doesn't mean she's going to beat Zoey the next time they battle or May for that matter.
I just hope the writers don't make Dawn cocky about her win. I don't mind if she get teary eyed everytime she looks at the Aqua ribbon, but I hope it doesn't go over her head.