While there are many types of exfoliants available on the market, chemical exfoliants are almost always preferable to physical ones. And of course, glycolic is the gold-standard of chemical exfoliants.
Physical (also known as "mechanical") exfoliation involves physically removing the dead cells from your face. This is often done by using a loofah, washcloth or cleanser with particles. The amount of exfoliation that you get from this method is directly proportional to the amount of time and pressure you put into it. This means that each time you use your cleanser, you will get a different result. Also, many people believe that if some is good then more is better. Thus, they scrub so hard that they cause an irritation or even break the skin and cause themselves to bleed.
Chemical exfoliation, on the other hand, is a more predictable and reliable way to exfoliate. Chemical exfoliants can be tweaked to exfoliate only a certain amount, and also provide the same results each time they are used, provided that they are applied to a freshly washed and toned face. This means that you can be sure that night-to-night your exfoliation is the same. It also allows time for you to see warning signs of irritation. Instead of immediate irritation, like that from a physical cleanser, there will be signs that the chemical exfoliant is irritating, such as flaking skin, before any real harm is done. And if you use a pH-adjusted and buffered glycolic product, you can be sure that it will be gentle yet effective.