How much longer does it take to drive a loaded moving truck versus a loaded car?

Well... it depends on how fast you drive.

Unless you have experience driving moving trucks, you'll probably drive slower than usual, because you'll feel less comfortable, you'll want to allow more distance between you and the other traffic, and you'll accelerate more slowly.

Still, say your move is 200 miles of mainly rural freeway driving. In a car you might average 70 mph and be able to make the trip in three hours; in a loaded truck you might average 60 and need to allow more like three and a half hours.

That's not allowing time to take breaks -- I always take more when driving a truck so that I stay that much more alert.