In DIY staging apps, you create the staging yourself. You move digital items around the scene, export the photos, and place them in your listings. With professional staging, you send an image in and they do all the rest of the work for you. This often produces more realistic virtual staging.
If you need to do advanced work, professional staging companies are usually better. For instance, a professional virtual staging company can actually remove existing furniture from photos and replace it with something new—hard to do by a non-professional.