I dunno, I trust a nice honest email with an attachment more than "some ethereal link to the Cloud".
There's no real reason (that I can see) to distrust the Cloud approach, and it is arguably a lot more efficient on several counts than the usual email+data attachment approach.
The thing to ensure would seem to be efficient and reliable backup/recovery of email and attachments.For local PC backup:
this can be achieved for Gmail and Gdrive by the use of:
(a) local backup of email via an email client app, and
(b) local backup of Gdrive via Gdrive Sync (though I am still trialling the latter in "discovery" mode, so it is not an absolute known quantity for me yet).