The CPS (Cumulative Patch Sets) approach used in Windchill is preferred over HotFixes used in Integrity for two reasons:
To make sure that all patches are installed. Patches are not supposed to break anything, so they could be installed at any time without too much validation testing by PTC customers.
To make the installation of new clients easier.
The current approach is especially annoying when doing an upgrade or when doing clean installs on new client machines because the user has to restart his client for every hotfix. This gives a very unprofessional impression. The desired approach is to have a method to include the hotfixes in the client installers, or alternatively have one single CPS instead of a collection of hotfixes. Given that CPS is a common approach in patch delivery, I assume that PTC would prefer that.