Glasses optical clarity is the best and as such glass lenses will have little to no distortion.Adding to that, it is the most scratch resistant optical material.However, glass will almost certainly shatter on impact. Plastic lenses are mainly made from polycarbonate and CR-39 plastic material. Polycarbonate is popular for lenses because of its high resistance to impact. polycarbonate lenses also have the highest distortion compared to any other material. CR-9 is another type of optical plastic. It has little distortion compared to polycarbonate. It is thinner and lighter than glass too.plastic being a lighter material makes plastic lenses much lighter than glass and therefore they are less likely to cause indentations.
Glass glasses and plastic glasses makes no diffrence on how sharp things look like. However, The advantage of plastic glasses is that they are much lighter and more duracle than glass glasses. Where as, they are much easier to be scratched. The glass glasses are hard to be scratched, but they are easy to get smashed.