Add Custom field in Base Data Entity in D365

Hi All,

i want to add custom field in base/standard Data Entity. For doing this work we have two approach:-

1) First Create Extension of Standard data entity and add custom field in data entity & also their staging table.

2) Create new data entity & add base standard data entity as a datasource in new created entity & also create their staging table for mapping.

So i want take the better option in both of them which one is better than other  and Why ?