Definitely take the bus to the MK, no question. If you drive you have to deal with the extra time of the monorail or ferry, while the bus drops you right outside MK.
We had a car when we were there last November (also stayed at the All Stars) and used it to drive to all the other parks. Typhoon Lagoon we had a front row space! If you get to the parks early, you can usually get a good space and the walk to the gates can be short. Other times, you are parked so far away that you need to hop on the tram to drive you from your space to the gates. Not a big deal, but you could have just taken the bus!
We are going back in December and considering not getting a rental car at all. I think the busses are that good.