This choice can be made by knowing what you are looking for. 1. If you have styled or curly hair, it is best to use satin bonnet so that you can tie your hair up with a scrunchie & cover with bonnet so that the curls or styled hair stays intact. 2. If you want protection from frizz and dryness at your own home, you should use satin pillowcases as they will protect your skin as well as hair. 3. If you are traveling/going on a vacation/sleeping at your friend's or relatives place, you can carry the bonnet in your bag and enjoy the satin benefits even when there are not satin pillows available.