I vote to for more functionality on the media side of things. I know I LOVE my xbox media center installed on my original xbox. In fact, I am keeping it just for the ability to play xvid, and such.
I have long wondered, why the people developing it just didnt go and make it an official xbox program. I mean I would gladily pay 60 bucks or more for that application. No need to mod xbox then.
I have never been concerned with the other "benefits" modding brings and would be happy to have a legitment app that gives XBMC functionality.