IF, you are referring to the "Memories" of an individual/person in "Family Tree" of 'FamilySearch'; and, an "Image" of a "Document" [eg. Certificate (Birth; Death:; Marriage) or something like], that you want to add as a 'Document'; THEN, ...
EITHER, both, are acceptable; and, work.
Here is a "Knowledge Article" in 'FamilySearch':
How do I upload memories to FamilySearch
I hope this helps.