My experience broadly echoes Glenn's recommendation; off for OLAP, on for OLTP. But, as you mention in the article no two workloads are ever the same.

These sorts of scenarios are perfect candidates for comparative testing using RML tools. Any critical system upgrade (hardware, firmware, service pack etc) should be subjected to a test run using a baseline workload, captured from a live system and replayed using OStress. While you’re at it, do a test run with HT enabled and disabled and see what effect it has on your particular system.