As a user of both of these lenses at one time or another, I can tell you that the IS version is sharper and takes a TC better if you plan on using it that way. Having said that, you are not going to notice much of a difference from the center of both of these lenses in real world shooting, just corners. To point out one more thing, if you print your pictures you will not notice a difference at all. This coming from someone that once had severe case of the syndrome.