JMeter
- Open source, active project
- Supports HTTPs traffic via HTTPS spoofing (works quite well)
- Supports various protocols other than HTTP, like JDBC to analyze SQL bottlenecks directly
- Supports cookie and session management
- Can be executed in distributed mode from remote host to prevent the host machine from throttling the test
- Captures screen (if specified) to be used as functional test (capturing screen is not recommended during load/performance tests)
OpenSTA
- OpenSource, not actively developed or maintained
- Support for HTTPS is patchy/unreliable at best
- Good scripting interface, better than JMeter for customization and parametrization
- Falls apart easily under load even in distributed mode
- Easy access for DOM objects to be accessed from scripts
- Monitoring of servers possible
HTTPerf
- Free, open source
- Command line tool (not GUI based)
- Granular support via command line options for inputs, delays, target throughput etc
- SSL supported
Grinder
- Very similar to Jmeter; Open source JAVA based record and playback tool
- Supports HTTP and HTTPS
- HTTP(S), JDBC, LDAP and more protocols supported
Mercury Load Runner
- Not inexpensive
- Method level Diagnostics on application
- Monitoring of servers during test built in
- Record and playback via GUI
- Not inexpensive :)
- Large scale/higher concurrency use, loads that JMeter cannot handle well
- More granular control over inputs and target throughput and output monitoring
