Provides more/better recovery options...
- After Exchange backup... if you have failure of EV, restore EV.
- After archiving run (with safety copies) ...if you have failure of EV, restore EV and perform another archiving run.
- After archiving run (without safety copies)... if you have failure of EV, restore Exchange, restore EV, then perform another archiving run.
IMHO... I would choose options that involve 'not' having to restore my real time messaging environment.
Also... adding safety copies does not delay moving the data from Exchange to the Vault... during the archive run EV will copy these items to the vault. With safety copies enabled it will only delay when it will actually delete them from Exchange and create the shortcuts in their place. (i.e. after the vault store is backed up.)
Also... the way I see it... you don't have multiple copies of the mailbox in the scenario we are discussing... you would have one... the most recent exchange backup... (unless you were doing a brick level backup or something like that as well as an IS backup.)
If you have the resources and backup window then... why not configure your vault stores to use safety copies?
Throw in Centera as your primary storage device as your primary storage that you have to replicate (instead of backing up) or implement snapshots of your EV data then safety copies becomes more important.
If you don't have the resources/backup window, don't see the risk of losing EV in that short time window as a likely/significant risk (which, admitedly is marginal) and/or still think safety copes are dumb.. then rock on.