Gonzalo Ayuso has posted the results of some performance testing he did with bind parameters in a PDO-based request for his application.

Some months ago a work mate asked me for the differences between using bind variables versus executing the SQL statement directly as a string throughout a PDO connection. Basically the work-flow of almost all database drivers is the same: Prepare statement, execute and fetch results. [...] What's the best one? Both method work properly. The difference is how databases manage the operation internally.

He gives two code examples, one with the bind parameters and one without, and the benchmark code he used to generate his statistics. It uses a PDO connection to execute several statements in a row both with bind parameters and without, measuring the time (with microtime) and outputting the results. His results show that while the simple update is faster, the bind parameter method has the added benefit of reusability for multiple queries.