The 'deleterevision' permission is an instrumental supply if you want to delete a revision of a page due to adding libelous information. But it also allows suppressing log entries and some sysadmins don't want to grant their administrators this possibility.
'deleterevision' as "delete a revision" is no additional possibility. Revisions can also be deleted with 'delete' and 'undelete' permission (but it's more difficult than 'deleterevision' process).
My suggestion is splitting 'deleterevision' permission into:
deleterevision: (un)deleting revisions only suppresslogentry: (un)hiding log entries only
Cheers, Tim