In terms of material used, there are two main types of contact lenses: soft and gas permeable lenses. Each of them has its own advantages and disadvantages. Soft contact lenses are made of comfortable gel like material that just fit on the eyeball. Soft contact lenses allow for instant ease and comfort for eyes. This is the biggest advantage of soft contact lenses. As for gas permeable lenses (hard lenses) are made of plastic that allows oxygen through the lenses and to the eye beneath. So, providing more oxygen to the eye and resistant to deposits of protein which could not finish by soft lenses are the best two advantages of RGP. What's more, if you have astigmatism, RGP may be the best choice. But they also have some disadvantages, they are not comfortable as soft contact lenses, and they need more time to get used to. If you want to go out for work with RGP, you will need another period of time to get used to them.