Backing up MS Cluster - Best Practices

Hi,

I have file server clusters to back up with BE 2012.  According to the Symantec article http://www.symantec.com/business/support/index?page=content&id=HOWTO74445, the recommendation is to do incremental backups using modified time as opposed to using archive bit.  Can I do a differential instead?  I prefer diff's over incrementals.

Also is there a need to backup the file server service or can I just back up the two nodes?  Seems like a duplication of effort.

Thanks