I am in an environment that relies heavily on SNMP traps and hardly uses syslog for event notifications. It seems to me that traps are pretty limited as far as providing details on events. For example an SNMP access denied trap only tells me that an SNMP auth attempt failed. Syslog tells me what caused the failure, like "community string T@11B0y unknown"
Do you have a preference for one over the other or are is it a judgement call depending on the specific case?