I have been using McAfee security products for about three years. The first package came with my new Dell computer. After that, I renewed each year. I don't recall uninstalling before reinstalling the new version/subscription. I thought when you automatically renewed, McAfee would remotely download the new version. This year I was advised by both customer service and the technial support to delete the current version before installing the new subscription.
The newest version is supposed to have it's own uninstaller, which cleans up previous versions, but it's considered wise to cleanup, use the MCPR tool and then reinstall if you are going from one year's version to the next, or if anything is different as far as which applications you are installing or if you are switching from a 3rd party version, such as Dell, to the McAfee direct version.