Hi Lee,
This really depends on what statistics you want to see. Security contexts will contain their own unique SNMP configurations. By configuring SNMP in the Admin context, you will only be able to poll MIBs for data that can be obtained through the Admin context. So, as an example, you will not be able to look at the CPU utilization of a context other than the Admin context, but you might see the resource usage statistics for the various contexts.
Hope that helps.
-Mike