Note: I am specifically discussing JBoss Developer Studio, which is Eclipse with some pre-installed plugins.
After years of evading any interaction with Java, I'm playing catch-up. Eclipse is proving crucial in minding the myriad details of Maven, class relationships, and the sheer redundant verbosity of Java syntax.
However, Java's fundamental nature can't be corralled by "just" a code editor. Don't bring a knife to a gunfight.
The basic difference between Eclipse and NetBeans is that Eclipse is more of a framework that hosts different language- and task-specific components; the Java editor and the Python editor are really different applications, not a single editor with different settings. Eclipse and NetBeans have different design philosophies, and that's fine. I happen to like Eclipse's philosophy.