I see the file permissions and ownership are slightly different between these two options.
Using Unraid Share, since no credentials are specified, files appear to use the uid and gid number of the user from the VM that created them (when viewing natively in unRAID). That is, if my user in the VM has uid/gid=1003 and I touch a file in the VM in this direct share mount, running 'stat' directly on unRAID shows the uid/gid as 1003 and permissions 0664 (rw-rw-r--). Since unRAID groups start at 100 and Ubuntu (for example) groups start at 1000, the gid for files are basically invalid for direct unRAID access (not that I think it really matters).
Using SMB share, files are saved using the uid/gid of the unRAID user account that is used to log in to the share. And they're also saved with 0666 permissions (rw-rw-rw-)
Which of these is preferable or does it not really matter?
I assume the two methods are equal in performance, i.e., the VM using SMB does not actually traverse my network but rather only uses the virtual network which (I understand) is equivalent to direct access.