Each of the three AJAX options has its own strengths and weaknesses, making each one suitable for different applications. The following table summarizes their strengthes and weaknesses:
The Java approach is capable of delivering good performance and functionality due to binary execution, multi-threaded computing, and the industrial strength of Java Virtual Machine. Applications written in Java are easy to develop and maintain because of the object-oriented programming nature of Java. It is good for enterprise Java developers who have Java programming skills. On the other hand, the Java programming skills requirement is also its weakness, because developer skill set requirements are higher than scripting. Historically, JVM compatibility in various browsers has been a significant issue for this approach. However, there are solutions available for these problems. One solution is to utilize a lightweight, JDK 1.1-compatible Java engine that is guaranteed to run inside all browser-based JVMs. This Java engine would abstract developers away from the traditional problems, enabling the development and universal deployment of Web applications by leveraging the strength of Java.
The Flash-based approach is good for applications that require a "sexy" look and feel. It is a natural option for graphics designers. Flash enables developers to create very rich user interfaces, given Flash's heritage as a "movie engine." To date, Macromedia has targeted Flash for three use cases in the context of applications: guided selling, guided forms, and dashboards—primarily consumer facing or data visualization applications. Flash applications can access Java and .NET objects running on the server asynchronously. The major limitations of this approach are ActionScript and the limited capability of the Flash engine. ActionScript is a proprietary scripting language developed by Macromedia. It is easier to do scripting than programming for simple tasks, but developing and maintaining many scripts is difficult and expensive for more complex applications. Flash is not an industrial-strength virtual machine like JVM or .NET CLR; as a result, there are functionality and performance limitations for Flash-based applications.
There is no doubt that all three approaches are viable and each has success stories to prove it. However, choosing the wrong approach for the job also can be devastating.