If you update the SNMP agent, you use the SNMP version of the dataprovider if you update the WBEM agent you use WBEM as a source. HP is in favour of the WBEM version but both are supported. Wbem only work on WIndows servers and later ESX versions. If you use Linux you can only use SNMP, most devices can only use SNMP (V1).
Using the SNMP agent you need to configure SNMP local and remote for the SIM server.