A servlet engine is a program running on a server that knows how to execute JSPs and servlets. E.g. Tomcat, JRun, IPlanet, etc

Features that make one servlet engine better than the other
  • Its fast and supports load balancing,
  • Provides a much better and more efficient SSL solution,
  • Provides a memory and disk based caching system for increased performance benefits,
  • Provides a number of reliability features, e.g. automatic server restart, detection and restart of locked or stalled servers, and monitoring of JVM memory usage,
  • Clustering provides the ability for multiple servers, thus providing enhanced reliability and allows sites to scale up as server demand increases,
  • Uses GzipFilter to reduce bandwidth usage and thus providing cost savings.
  • etc...etc....

 How would you go about choosing one for your organization?

This will depend on the organization’s need and/or the following:
  •  Its flexibility and ease of use,
  • Plug in capability and integration,
  • Scalability: clustering, caching, etc.
  • Security with OpenSSL solution minimum,
  • Reliability: ability to detect error & monitor memory usage.

References:
http://www.servlets.net/company/news/servletwatch/resin/index.html

http://www.caucho.com/

http://caucho.rz.klopotek.de/resin/doc/overview.xtp#cluster

http://blogs.webtide.com/jetty/files/articles/jetty-v-tomcat.pdf

Jetty Servlet Engine Cross Site Scripting Vulnerability
http://www.juniper.net/security/auto/vulnerabilities/vuln5821.html

http://jetty.mortbay.com/jetty/