We've always stayed on-property, driven to WDW in our own car, but taken the bus to the parks with only outlier exceptions.
One exception was getting to a dinner ADR at Chef Mickey's from the Swan on our very first day of our very first trip to WDW in 2001. The other was on our last day in Orlando one year, and we opted to get one last ride in at Soarin' early before we left. There was another time that, for reasons I frankly don't remember, we drove to MK, not realizing that doing so takes you to the TTC, so I wouldn't do that again.
If you drive and park-hop, you have to allow for the time to get from the 2nd park back to the park where your car is located, which can be a hassle, esp with a load of tired kids or family. OTOH, if you're someone who just doesn't like buses, then driving makes sense.
In general, to each his own, but I give the nod to just letting Disney burn the gas I've already paid for and ride the buses unless there's an overarching reason to drive.