If you're only using the screen for guidance and there won't be anything else hooked to it (autosteer, section control, rate control etc) it will probably work fine to hook it to the cab power supply.    The big issue about going to the battery vs cab power supply comes from having other stuff hooked to the screen that draws a lot of power which sometimes the cab power supply is inadequate.


What I don't like about being hooked to the key is that every time the key cycles you're going to have to wait for the screen to reboot and re gain GPS signal.   Which may or may not be an issue for you.   I consider it an avoidable nuisance.