I think that Cody did show more emotion in his solo than he had at any point during the show, and it was precisely that "transformation" that made them pick him for the win. Mochi, in effect, lost because she was too good all along. Therefore, she didn't show the same improvement Cody did. If only Mochi had sucked a little more along the way and then used their advice to magically get better at the end, she probably would have won...