Going from any resort to/from MK, driving vs. the bus system is more or less a wash. The bus might be slightly faster on average, but driving is much more predictable. Driving between any resort and the other theme parks will be more predictable *and* faster than taking the bus, on average, but only by a little bit. Driving between any two other destinations* will be much faster in your own car, but such trips are rare for most people.
So, you can save a little bit of time in your on car, but not much in the grand scheme of things. So the way to decide is to ask yourself: what sounds more like a vacation to you?
1: Never having to touch your car keys or navigate in a slightly unfamiliar space?
2: Never having to wonder when the bus will come and/or whether you'll have to stand?
The answer to that tells you whether you should drive or ride.
I don't mind navigating, and I dislike the uncertainty of the bus system, so I tend to drive most places---even to MK about half the time, though I always let Disney do the driving if I'm having a second BEvERage with dinner.
*: I'm not sure about DTD these days. Mostly, I plan to avoid it until the construction is done.