Soft Delete: property or separate collection?

We are wanting to add support for soft deleting documents in one of our collections, but we are debating between two approaches:

  • Property indicating document is deleted
  • Moving document to another collection, such mycollection_deleted

The first is the easiest to implement, while the second keeps out deleted documents from searches.

I have seen both suggestions, but I am not sure whether there is a preferred approach in general MongoDB database architecture?