The biggest differences normally arise with multiple queries running concurrently. For example, InnoDB & PostgreSQL use MVCC whereas MyISAM uses locking, and

The biggest differences normally arise with multiple queries running concurrently. For example, InnoDB & PostgreSQL use MVCC whereas MyISAM uses locking, and PostgreSQL normally wins most benchmarks with high concurrency on multi-core machines (8+). I'm not certain I understand what you ran in the 'heavy' and 'light' threading tests. Can you provide some more details / explanation?