One of the benefits to painting before you move your furniture in is that you have all that open space to use effectively without any concerns of dripping paint on your valuables. At the same time, you don’t want to risk dinging up that fresh coat of paint when the time comes to move all your furniture in.
Here’s a simple tip to consider: Make doorways and stairwells the last thing you do. In fact, after painting your rooms, go right ahead and move the furniture in and design the room to your liking. This allows you the (hopefully) occasional slam into the wall on the way up the stairs, or a bounce off the doorjamb on the way into the room. Then, once all your furniture is sorted out in the respective rooms, go ahead and finish up the doors and stairwell.
Not only will the paint look fresh, but you’ll save yourself any extra work along the way.