This is always the most difficult question. Eclipse has been I think the most widely adopted IDE at the moment. It has the maximum support for plugins. In fact at the moment it is the first IDE for which plugin is supported. Netbeans is also fast catching up with its feature list. If you are in the crossroads and wanting to adopt an IDE than look around your peer group. As they can help you out the the IDE that they are working with.Also I think most of the IDE do smell and taste similar once you get into one. Some of the thumb rules that can help you out:
- What features and frameworks you are going to use in your application? Check what is the support for those features in terms of plugins.
- Which server are you adopting? If you are adopting one of the popular servers than most of the IDE has first citizen support for them. However if you are using one of the lesser known servers than you might want to check that.
- Is there plugin support to your Source code control system? I think this is important in terms of productivity.
- The similar question can be asked about Project management environment. If you need such kind of integration and if it is available.
- Check how active is the community around that IDE. You might not want to get into an IDE in which active development is not happening.