If you're staying at a Walt Disney World Resort the bus would be a lot faster becasue it drops you off right by the entrance to the Magic Kingdom. If you were to take you're car you would have to 1st park at the TTC, take their tram and then either take the Express Monorail or boat to the entrance of the Magic Kingdom. So I say use Walt Disney Transportation buses, that is if you're staying onsite and not offsite.