I liked this list more than the novels but less than the novellas. There was one that I felt definitely should not win, and my top vote is not very far ahead of my fourth.
5) "Rat-Catcher", by Seanan McGuire. This was the story whose failure to spot the difference between Irish and Celtic, combined with anachronistic expressions, annoyed me last weekend.
4) "The Boy Who Cast No Shadow", by Thomas Olde Heuvelt. An interesting concept, a tragic love story between two kids who are different from the rest - one made of glass, the other transparent in a different way. Marred by some misprints and infelicities of expression which should have been caught by the editor (eg "fuckup up" for "fucked up").
3) "In Sea-Salt Tears", by Seanan McGuire again. Like "The Boy Who Cast No Shadow", a gay love story in which our protagonists face additional problems through not being exactly human, in this case shape-shifters with a difficult family heritage.
2) "The Girl Who Went Out For Sushi", by Pat Cadigan. Story of post-humans exploring the moons of Jupiter, and the girl who wants to be like them. Some glorious use of language, and I may yet change my mind and put this first. It's also the closest the list comes to traditional sf (not a recommendation necessarily, but an observation).
1) "Fade to White", by Catherynne M. Valente. A series of vivid vignettes from an alternate history where McCarthy became President and infertility is widespread due to nuclear war; American society is constrained to promote reproduction. I don't always like Valente's style but this largely worked for me.
See also: Best Novel | Best Novella | Best Dramatic Presentation (Short Form)