Depends on where you're staying and where you're going.
Going to parks - If you're staying at a value or a mod, or OKW or SSR, your car will be reasonably close to your room and easy to get to, so I would say it's easy to drive to Epcot, DHS and AKL. At the deluxes, there is usually a pretty long walk from the parking lot to your room, and the bus stop will definitely be closer (unless you use valet parking).
Going back - For us, we prefer to drive and walk out of the park and go right to our car. If you don't park within walking distance of a park entrance, there is usually a tram to take you to your car within 5 minutes. Sometimes the wait for a bus can be 20 minutes or more, depending on the time of day. That is really frustrating when all we want to do is go home.
Magic Kingdom parking is not at the front of the park, you have to take a ferry (recommended) or monorail to the park front. The ferry dock is the closest transportation to the front entrance, the bus and monorail are probably equidistant further away on either side. We prefer driving even to MK vs. a bus for the same reason as above - we can usually get on a ferry right away or within 5-10 minutes to our car. Trams run constantly at MK, so we're at our car, sitting down and relaxing vs. standing in the bus serpentine.
The only time we don't drive is when a boat is an option, from Fort Wilderness. That's the best!
However, some folks just like to take their time and take a bus. I would recommend trying it and deciding if you like it. I also believe that when you know a car is an option, you have less patience with the bus system. That's what happened to us