nfs and cifs should be expected to have about the same overhead in protocol on a per-packet basis, so about the same potential for transfer rates.
the performance of the disk tends to be the file system on the disk. windows ntfs is not known for performance when dealing with the filesystem and as such usually has less performance than a linux based filesystem normally used on nfs shares.
the device you mention is actually a linux nas so it will have an ext3 or ext4 underlying file system using samba for smb, so you could expect the performance to be about the same on that device.
i looked for a long time for an nfs supporting nas/san at a resonable price and came across the QNAP line of san devices. they offer 2 bay up to 8 bay models, having dual nics and offering lots of protocols like iscsi, nfs and smb.
the part i like about it best is that when you create a new share on the san it can be accessed both by nfs and smb (not a good idea to do that at the same time of course). so i can create the destination disk on the san in an esx connected datastore, do the backups, shutdown vDR and from windows copy/backup the file elsewhere, then startup the vDR appliance again. with some scripting on the windows side this can be done by a schedule if need be by using vmware powershell or vmware cli to stop and start the vDR appliance.
the performance of the QNAP is outstanding, for single transfers it normally runs about 80% average on a 1Gb link and 100% when copying the vmdk files. if you have more than one activity going on and the QNAP nics are configured in load balance/failover mode then you can easily exceed 1Gb data transfer rates on the QNAP by using both nics.
i also have one customer using the qnap as their production san for a 2 node esx cluster with 6 virtual machines running (2 x dc, 2 x exchange DAG cluster, 2 x fileserver running DFS to keep the files in sync) using a 6 bay QNAP in Raid6 on 2TB sata drives.
some models are not vmware certified so be careful in choosing, the main difference in certified or not is the nfs selective presentation in controlling which hosts can connect to the nfs share, without certification you only need the credentials, with certification your host ip must be specified on the qnap to be able to connect (unless you leave it at * for everybody)