Methods to set access to all mailboxes

Hi,

can someone tell me the difference between these to methods?

Get-MailboxDatabase | Add-ADPermission -User USER -AccessRights GenericAll

Get-Mailbox | Add-Mailboxpermission –User USER –AccessRights FullAccess

Using the first Command also adds the User in the EMC to the "FullAccess-Guys" an for Example using Outlook, you are able to open other Mailboxes and read,write, delete stuff so. 

Ive noticed, that the first wont work with Netapp Single Mailbox Recovery, the second one does.

I would prefer to set the accessrights on database level, so you do not forget the new mailboxes but unfortunately this is not posible.

thanks for your help!