Correct butty.
I prefer to keep it as a script as i like to see what a kernel's default settings are straight after flashing. I don't know if the kernel cleaner script would reset these settings if booting as a service as I don't know how
Voltage control stores and run these service settings. If they are stored in cache areas then yes they would also get wiped by the kernel cleaner. Best way to find out is to try it and see when happens.
The benefit of doing it as a service is that the settings you specify will not get overridden by other potential voltage/governor adjusting scripts.
Edit: when stored as a startup service, a default profile gets applied after media scanning completes, so voltage control settings will apply even after a kernel cleaner script run. I can see both advantages and disadvantages to this.
I'll have a look how voltage control stores and runs this service and may produce a new version of the cleaner script to reset this.