Most of the time I have preferred HDR over flash photography indoors when there is hardly any natural light entering the room. Exterior is totally different. I would always use HDR for exterior real estate photos.

Look at the 2 examples and I will explain why HDR is so much superior to conventional flash photography. I even use rear curtain to reduce the shadows and reflections. That is the best single interior flash photography gets in rooms that don't have a natural light source. Very important: No natural light source because if you take a shot through a window it is always a great idea to take an extra photo with flash for the window view.

Compare the shadows and the depth of the floor and you will notice the most significant differences. Also keep in mind that I used Rear Curtain Flash with Softbox. You can only imagine how the ceiling shadows would look like when using ordinary flash.