Sync relationship fields using keywords, or custom meta-data in Scrivener?

I’m tinkering with my sync setup for a Scrivener project, learning as I go. I want to be able to use Aeon’s Subway Map view, so I’ll be using the Story Arc field for each of my events. For my sync set-up, I need to choose between syncing Story Arc in Aeon to a keyword in Scrivener, or to a custom meta-data field. Can anyone clue me in on the advantages and disadvantages of each of those two approaches, please? This will also help me resolve the same sync design question for theme, character, and location. Thanks for any tips.