I think you are missing the whole point here about the advantage of Wubi. With Wubi installation of Ubuntu / Mint Linux, we can uninstall these flavour from Windows OS just like any other software. In case of Sabayon, we may have to create a partition and install. For newbies, who would like to test Linux, Wubi would be a good idea since they can safely uninstall it in case if they face any problems. Having an escape door will prompt them to test Linux instead of having to install Sabayon on a different partition and scratch the head for uninstalling it later without having to fiddle with the MBR.