There is two available Eclipse plugins for Maven :
m2eclipse seems to be the oldest but the more robust. Is there any key differences between the two ?
Which one should be chosen for a project starting today and why ?
I choose m2eclipse since it is stable and have all that I need. Especially ability to resolve dependencies inside workspace.
I tried the other one some time ago and didn't like it. It was to buggy so I gave up quickly.
I used m2eclipse. But I did never manage to launch the tests or the whole project from within eclipse (the project had nested folders for various sub-modules). When I used it they said support for that was experimental. The most I could get was syntax-checking and such. For the rest I used the console.
Did not like the experience at all.
For me as a complete Maven-newbie the m2eclipse plugin worked quite well. We manage around 15 projects with it. The nested Maven projects will be flat in Eclipse (as it does not support nested projects), but all of them were automatically set up the right way, so everything works fine. Up to now I never needed to manually invoke a Maven command, for me using the preconfigured "run as" launch configurations did their job quite well.
For me the quality of m2eclipse can be judged by this simple example: If you run Eclipse on a JRE instead of JDK, m2eclipse shows a warning that some of its features rely on a JDK. Nevertheless it still works on the JRE. And the warning dialog has hyperlinks to the Eclipse documentation about command line arguments and to the "Installed JREs" preferences, so you can easily fix the wrong Java VM.
That said I cannot speak for or against IAM, as I never used it due to the good m2eclipse experience.
Side by side comparison of Maven plugins for Eclipse. It haven't been updated to recently added features. For example, see New and Noteworthy page for m2eclipse.
what about multi modules project ?, m2eclipse plugin is ineffective. Especially if we use war module.
The side by side comparison is moved to http://docs.codehaus.org/display/MAVENUSER/Eclipse+Integration%2C+Eclipse+Integration
Why are you guys use Eclipse, anyway? Maven works as it does. OK, you want to use it in a IDE? for productivity? Use Netbeans! It doesn't have to import. It doesn't create . files. It seamlessly integrate maven project. Actually Netbeans see the maven project folder which has pom.xml inside it as native project.