The Virtual Background Systems are based on optics. They do not involve a computer, software, and there is no time-consuming post-production work. The Virtual Background Systems are designed for producing high quality portrait photography. Green screen and blue screen, also known as Chroma key, were designed for television and Hollywood film-making.
With the Virtual Background System, the photographer sees the subject and the background live as they compose the image. When the shutter is released, the background and the subject are captured and the photograph is complete and ready for instant viewing. There is NO post-production work.
With green or blue screen, the photographer sees only the green or blue background. The subject has to be posed generically and then after the subject has left the studio, the photographer has to paste in an appropriate background for each image. This is exactly the reason green screen backgrounds look pasted in…because they are pasted in. Plus, this takes time, a whole lot of time. If the photographer shoots 50 proofs, they have to paste in 50 backgrounds, one at a time, which could take hours if it is done right. With the optical virtual background process, the process is all done when the photographer takes the last exposure.
With green or blue screen, there is also the problem that comes with the subject wearing a color that technically mixes with the background. For example, if the subject is wearing anything green with a green screen background, that which is green may be replaced with background! It is also highly likely to get green or blue fringe around the hair. With green or blue screen, considerable extra work has to be done to clean up an image including the possibility of having to do re-shoots when problems are so severe that they cannot be cleaned up. Although some school photographers are using green and blue screen, their life would be much easier and their results better if they used optically based virtual backgrounds, not to mention how much virtual backgrounds would reduce their cost. But, if one really wants to use green screen, you can use your virtual background system to project the green or blue color to achieve better results.