WE go to WDW a lot and I learned a few years back, it is much better to take WDW transportation to the parks than to drive to a park. Sometimes the bus ride and wait can be a bit longer, but it's all relative.
If you drive by the time you walk to your car in the parking lot or wait for a valet to pick it up and then drive to the park (and wait behind all of the buses!! LOL!!) and then park in the lot and then either walk to the entrance from your car or take the tram...most of the time DRIVING is longer!! (we've been there, done that)...
Once the bus picks you up it does make some other stops sometimes but it takes you MUCH closer to the entrance and if you're going to MK you don't have to take the monorail or ferry which is an additional 15-20 minutes minimum added to what I said above.
The only exception "may" be FW if you have to use the internal buses. Since you have to take a bus to the front (or boat from the dock) & you don't have a golf cart it can be time consuming HOWEVER that being said, drive to the front if you have a car and park near the buses if you prefer--this is where we learned it was longer to drive to the park!! We went to Epcot and parked what seemed like a mile away from the entrance. We just missed the tram so we walked it, it was a long walk.
NOW, DTD or to a resort--that's a whole different story, drive. Although, from SS, DTD is probably a quick hop on a bus (or boat ride??) Because with the resorts, you have to transfer buses at a park or the TTC or DTD. That can take a long time.