I prefer to drive.
It's not just a matter of time savings, although for most destinations at WDW driving is quicker than the busses, but it's also a matter of comfort level.
Here are a few pros and cons, at least from my perspective:
Bus:
- Gotta wait up to 20 mins for the bus to show up
- Gotta wait up to 20 more mins for the bus to load and unload, especially if there are folks in wheelchairs or
ECVs
- Busses are often SRO, forcing me to stand up through the entire ride (last time I stayed at Pop with no car I stood up on 75% of the bus rides I took)
- Busses often make multiple stops, taking much longer to get where you're going
- At the end of a park day, bus waits can often exceed 45 mins
Car:
- Wait for the parking lot tram is only 5 minutes or less most of the time, and I often park close enough to walk directly to my car anyway
- No wait for loading; get in and get moving
- No standing in my car; I always get a seat
- My car goes exactly where I want; no multiple stops
- At the end of a park day, the wait for a parking tram is way shorter than the wait for a bus, and there is seldom much of a delay in getting out of the lot
Keep in mid that these observations are based on my personal experience, which is mostly in the off-seasons, although I have been to WDW in May and June a few times.