This is really a matter of personal preference. Many prefer to let Disney do the driving. Some are intimidated by driving in an unknown location. Some prefer to use Magical Express and the WDW transportation system to save money. Some consider buses part of the vacation. Everyone has to do what works for them - one method is not empirically better than the other.
For me and my family, we drive. (Even to MK, though some will tell you you're better off taking WDW transportation to bypass the TTC.) We like having our own car, being on our own schedule and going where we want to go. I like the fact that we can control the a/c (buses are always frigidly cold to me) and the music, have a place to leave some items, the ability to plug in a cell phone for a bit of extra juice, and we are always guaranteed a seat. If we're leaving Epcot and decide we want to grab Chick-Fil-A for lunch (we can't get this at home), then we can just drive over there before going to the resort. We do much of our dining out at resort restaurants and find a car invaluable for getting to these locations.
I have taken 1 WDW bus in my last 4 trips, and I don't feel like I'm missing out on anything. We wouldn't do it any other way.