Is there any special reason you want separate installs for the two different desktops? You can install both desktops (or even more, for example also KDE) in one installation. You simply choose which desktop to use, before you log in at the login screen. Click on the wrench on the login screen, a popup will show, select the Desktop environment you want to use, then log in.
You do not need separate installations to do this.
You can do this with the “Distributor” setting in Yast boot loader. For 13.2, I used the default “openSUSE”. In a separate install, I used “factory”. The name of the directory used in the EFI partition is the Distributor (or the first word of the Distributor).
Just run Yast bootloader from within your system. You can cancel out, to avoid making actual changes. You should see the “Distributor” line on the opening screen (left tab). It just sets the “GRUB_DISTRIBUTOR” line in “/etc/default/grub”, and the installer uses that to determine the name of the directory in the EFI partition.