Maybe I don't understand what you are seeing.

If you set the printer as default through the GUI, the registry setting will match the case. If you use Kix and do not match the case exactly as the gui, it will cause the issue that the poster was having. In other words, kix sets the registry setting to match what you type in the script, not what is in the GUI.

Wscript somehow knows that if you do not match the case of the gui, it will transform it in the registry to match.

Does that help?