Mail Drop is a better option because it doesn't send the document itself across email; it uploads the document (temporarily) to iCloud, then sends the recipient a link that will allow them to download it from iCloud at their end. The end result is the same, but it avoids having a large file taking up space in their email inbox.
Here's what it looks like to receive a Mail Drop email. You'll see that there's a deadline in there: the file will be deleted from iCloud after 30 days.
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