It depends on the park.
For the MK, it's a schlep to drive.You park in the TTC, take a tram to the actual TTC area where you get a monorail or boat to the MK.IMHO, the bus is better...drops you off practically at the gate!
For the AK, the parking is right there, and the bus drops you off right there...there's no taking the bus to the boat to the train to the plane, so either is probably OK, with car maybe slightly better due to no waiting.
For MGM, you park and take a tram to the front entrance or the bus drops you off at the front entrance or the boat from the BW area drops you off near the front entrance. Again, not terrible any way you do it...car maybe a little more convenient due to no wait for a bus. The trams run frequently to get you out to the parking lot.
For Epcot, you take a bus that drops you off at the front gate, or a tram from the parking lot to the front gate. Same scenario as MGM.If you're at the MK and want to go to Epcot, there's a monorail that runs...pretty cool. But of course, if you drove to MK than you have to get back to the TTC once you're done at Epcot.