Slides present their own problems. Other than physical damage like scratches they sometimes attract mould and dust, they also fade and discolour. It is also known that certain film makes and types gave a blue or green cast to the picture.
Projectors are usually stored out of easy reach and replacement bulbs can be difficult to find. Once scanned most DVD players will allow viewing on your TV.
Some slide scanners offer a system where it attempts to remove dust and scratches. In our experience this reduces the sharpness of the scanned image, especially if an enlargement or TV viewing is required. To achieve the best results we lightly clean the slides prior to scanning and remove specific damage afterwards digitally. Because of the size of slides they are scanned at a higher resolution so that they can be enlarged to give excellent results.