It depends on your GPS , how you use it, and your preferences. Plus does your GPS have any quirks you are aware of when navigating longer tracks etc?
I prefer to just follow a line on the map with no prompts.
The problem with a single full track is that north and south overlap but unless your gps shows arrows on the map it would be easy to pick up the southbound route when you meant to follow the north bound route.
The stage by stage tracks ensure you don’t miss a control , but it’s pretty hard to miss an LEL control anyway. You will have to load up a fresh track at every control. In a tired state you may load up the wrong track or it may be possible you didn’t load all the tracks on your gps before you left home. It is additional mental load you may not want in a fatigued and sleep deprived state.
The tracks of 300km each, where do they end? I’d hate nothing more than the track just ending in the dark in the middle of nowhere, at night, between controls.
My preference is to load a single north bound track, followed by a single southbound track. Plus have waypoints with alarms for all the controls. My gps remembers the track it was navigating even when switched off, for instance if I’m sleeping. Thus I can just switch it back on and I’m good to go. Only needing to load a fresh track at the start and Dunfermline. Minimal mental load when it comes to navigation.
Anco De Jong in 2017, used the single northbound and single southbound tracks. Not that that should influence your decision.