http://carinae.net/2010/06/benchmarking-hibernate-validator-and-apache-beanvalidation-the-two-jsr-303-implementations/

Apache BeanValidation

Formerly Agimatec Validation, since March 2010 it has migrated to Apache where it is currently under incubation. One of its most useful extra features is the ability to perform method validation using the same kind of JSR-303 annotations.
The benchmarked version is: 0.1-incubating.

Hibernate Validator

The reference implementation of the standard, coming from the JBoss people. Amongst other extra features, its 4.1.0 release will allow modifications to the constraints definitions in runtime via its programmatic constraint configuration API.
The benchmarked version is: 4.1.0.CR1.

Conclusion

Several conclusions can be extracted from the results:

• Apache implementation is around 50% faster when validating under these scenarios, and so, it is likely that using it will improve your application’s performance compared to using Hibernate’s Validator.
• Both implementations performance scales equally from 1 thread to a multi-threaded scenario with 4 threads.
• Parsing time is roughly equivalent, but this shouldn’t affect your application performance as much as validating performance.
• The relation between the performance of the two implementations doesn’t change while going from a simple scenario to a more complex one.