Plastic frames often have no nose pads and metal frames have nose pads. If you choose plastic frame, you need to make sure they fit your nose properly so that they can't slip down from your nose very often. Metal frames with nose pads are adjustable to fit your nose properly, but when you take off them, there will be marks on your nose. So it just depends on which one will fit your nose perfectly.
Glasses without nose pad are usually good for people with a Roman nose so that they will not slide down frequently. But glasses with nose pads can make you feel pressured on the nose and give you a headache when wearing for a long time.