[drpizznock]

What would be a good reason to use MrMC on the Shield instead of Kodi?

You know your environment and needs better than anyone. If Shield is your only device then consider the approach Kodi takes to their product vs. MrMC. For example, I don't use MrMC, because at this time I need to provide a consistent look, feel, and function across different hardware platforms. I've been able to accomplish this with Kodi before Shield or support for the android platform even existed.