Which technology suits your RIA project?

AJAX
This technology appeared to balance the growing popularity of Flash. While creating sites only some elements of it are used e.g. it has no such visual effects as Flash has and uploading AJAX pages takes much more time, besides it is not convenient for programmers. In general, AJAX pages look like common HTML pages with the only difference in periodical partial updating when necessary by means of JavaScript.

Flash
This is the most common platform in the Internet. It is by far the best variant in case of developing applications for end users in the Internet, i.e. projects to be looked through by any users through their browsers.

Flex
Flex technology outperforms Flash. According to many parameters, it is a kind of Flash sequential based on the new version Flash9. However Flash9 itself is under development now, and its complete utilization in most computers might well take about 2 years. During this period it is likely to replace old Flash applications.
At the moment it is best suited for desktop applications which will be provided with a Flash player.
The situation with Flex closely resembles that of Flash7 and Flash8 with the latter being better but not very common. The difference between 7 and 8 versions was not as great though as between 8 and 9.
Moreover, Flex is only an addition to Flash with components for creating applications quickly and easily.

Java
It would be a good competitor for Flash or Flex but it is supported only partially or not supported at all by most browsers, unfortunately. Often Java is switched off for security purposes. It has not been applied widely enough. In addition, your application developed in Java will not look as attractive as it would look in Flash or Flex.