For me personally, I drive a lot on a daily basis. I mean, a ton. And we usually drive to Walt Disney World as well. When we get there, I like to park the car and leave it. Normally, the only time we move it for the entirety of our vacation is to go to church on Sunday morning. I am quite content to take Disney transportation everywhere and not have to drive.
For others, though, I know they don't care for Disney transportation and/or prefer to use their own car.
I think it all comes down to what your personal preference is. With either form of transportation, if you know what you're doing and plan correctly, you can get where you're going and get there when you want to be there. It's just what works best for you personally.