They are of course in many ways comparable; of necessity web services frameworks must fill in all the same blanks, but since both projects are very young, each has certain areas that are more well-developed than others. The chief differences are as follows:

  • CXF has support for WS-Addressing, WS-Policy, WS-RM, WS-Security, and WS-I BasicProfile. Axis2 supports each of these except for WS-Policy, which will be supported in an upcoming version
  • CXF was written with Spring in mind; Axis2 is not
  • Axis2 supports a wider range of data bindings, including XMLBeans, JiBX, JaxMe and JaxBRI as well as its own native data binding, ADB. Note that support for JaxME and JaxBRI are still considered experimental in Axis2 1.2. CXF currently supports only JAXB and Aegis; support for XMLBeans, JiBX and Castor will come in CXF 2.1
  • Axis2 supports multiple languages–there is a C/C++ version available in addition to the Java version.

In comparing these frameworks, though, it’s just as important to look at their approach to developing web services as it is to compare features. From a developer perspective, both frameworks behave very differently from one another. Axis2 has taken an approach that makes it in many ways resemble an application server in miniature. Axis2 comes packaged with a WAR that can be deployed on a servlet container such as Tomcat that is designed to make web services easier to manage and deploy on the fly. The Axis2 Web Administration module allows Axis2 to be configured dynamically while applications are running–new services can be uploaded, activated or deactivated and their parameters may be changed. The administration UI also allows modules to be enabled on one or more running services. The only downside to using the UI for these purposes is the fact that configuration changes made through it are not persistent–they go away when the servlet container is restarted.

Axis2 lends itself towards web services that stand alone, independent of other applications, and offers a wide variety of functionality, and a good model for adding more functionality as time goes on through its modular architecture. Some developers may find that a little too cumbersome or heavy-duty for their needs. These developers might prefer to look at Apache CXF.

CXF concentrates on developer ergonomics and embeddability. Most configuration is done via the API instead of cumbersome XML files, Spring integration is heavily emphasized, including support for Spring 2.0, and CXF’s APIs and Spring configuration mirror one another fairly closely. CXF emphasizes code-first design, using simple APIs to make development of services from existing applications easier (and its embeddability helps too).

Whichever framework you choose, you’ll have the benefit of an active and stable open source community. Each of these frameworks has corporate backing: Axis2 is backed by WSO2, and CXF by Iona. Both have lively developer communities. Axis2 has been around longer but CXF is catching up quickly.
My recommendation is this: If multilanguage support is important, Axis2 is the clear choice. If you care about an implementation focused on Java with tight integration into projects like Spring, CXF is a better choice, particularly for embedding web services inside of other programs. If the new features in these projects are not important, and you’re relatively happy with Axis1, you should consider staying on this and keep up with the latest maintenance releases until you have a business reason to migrate.