From a bodybuilding perspective, if you have all the time in the world to focus on tiny little details in your development, seated is probably slightly better. From and athletic perspective standing wins every time. Guess it depends on what you're goals are.
I perfer standing because of all the stabalizer muscles it works, like abs, obliques, and back. Those are all the hollywood muscles I want to work anyway. Plus, I dabble in some strong man competitions as a hobby, so I need the stabilization work.