Hey Laurence,
I'm not sure what you mean by NW SSO SNC vs ABAP SNC.
Check out this:
Important BLOGS:
--> Nice blog. Good detail on how to use kerberos to do SSO purely for SAP GUI for windows
using SNC
NOTES
1912175 - SAP Single Sign-On 2.0: Central Note
--> central note for SSO 2.0
--> lists a basic explanation, relevant notes, suite of products, relevant components...
Hope that helps.
NICK