I generally hate Disney bussing, so I definitely prefer to drive to AK, DHS, and Epcot.
For Magic Kingdom, I'm torn. I hate having to wait to take the parking tram to the TTC, then wait to take the monorail or ferry to the park, and then do it all over again when we leave. At that point, I think the bus might have a very slight edge, depending on our other plans for the day.
My favorite option is valet parking at a monorail resort, then just taking the monorail to the Magic Kingdom. Of course, that's $15 plus tip each day you do that, so it can't be a routine thing for us.