Here's a benchmarking exercise I found: https://www-staging.commandprompt.com/uploads/images/Command...

With a tidy summary:

> Any application with a high shared buffers hit ratio: little difference. > Any application with a high ratio of reads/writes: little difference. > Data logging application with a low ratio of reads/inserts, and few updates and deletes: little difference. > Application with an equal ratio of reads/inserts, or many updates or deletes, and a low shared buffers hit ratio (for example, an ETL workload), especially where the rows are scattered among disk pages: expect double or greater CPU and disk I/O use. > Run pg_dump on a database where all rows have already been previously selected by applications: little difference. > Run pg_dump on a database with large quantities of rows inserted to insert-only tables: expect roughly double CPU and disk I/O use.