I own the Clarisonic Mia in Lavender, which I purchased earlier last year, when my skin started to breakout. I actually recently purchased a new brush head for the device. I love it and find it to be a wonderful device. I have used my Clarisonic with several different cleansers, including the three cleansers for different skin types that Clarisonic sends with the device. It is easy on the skin and definitely delivers a cleansing regime that is easy on the skin (it massages your skin, as it cleanses).
The Olay device is more like the Conair device that came out a while ago. I, myself, haven't tried it, however; a few friends of mine have, who also have used the Clarisonic and they all have told me that it is not nearly as good as the Clarisonic device. It is relatively commercial more so than high-end. It is decent, but it's a little more harsh (some may not find it harsh, but everyone who has used this can agree that it is not as gentle as the Clarisonic, I have been told) and definitely not as good as the Clarisonic. The Clarisonic's strengths exceed Olay's Pro X system. From what I heard, the only thing that is appealing about the Olay Pro X system in comparison to the Clarisonic is the price.