Oxford Comma vs. No Oxford Comma: What Writers Should Know

Which is the best for comma usage in fiction?

To be, or not to be? 

As I’ve been revising and editing Another Past: Book One, I’ve run into an inconsistency in my editing tools. In the review tools built into Ulysses, where my definitive content lives, Oxford commas are used. This suggests a comma before the “and” in a list of items or phrases.

In MS Word, which I use for final formatting before uploading to Amazon, the syntax tool says the comma before the and is not needed.

For this edit, I’ve decided to use the Oxford comma, since it makes the intent of the dialogue and narrative more clear. What do you think?