Security Product Selection: NIS vs SEP vs SEP Small Business

I am looking for a selection guide.  I have been deploying NIS for 99% of my customers.  I have one client who is using SEP Small Business - until a month ago, I had no experience with it.  I have used SEP in the past.  Does a document exist that will enlighten me to the features and functions of each?    Could someone provide a rough idea of the differences?

At this point I have segregated their use purely by client size and configuration:

1 to 5 PC's - Norton's Internet Security

5 to 10 PC's, Workgroup, NO domain - SEP Small Business

Domain - SEP

Thanks,