Final Word: Shinzou
I decided on Shinzou mainly for his mastery of grammar/spelling, as well as dominance over the battle-field. This is in no way reflective of Mashiro's skill as a Shinigami, but Shinzou was able to maintain a steady lead in all cases and has the role-playing skills to back up that edge.
Suggestions:
To Mashiro, I would say work on that grammar just a little more and look for a spell-checker of some sort. Other than that, don't rely on Kidou as much and be more offensive.
To Shinzou, the only potential hazard I can see is you should get more into your opponents face. Past that, you're fine.
Good job to the both of you! smile