If you are good with one, you will not have any problems with another. Both Netbeans and eclipse are feature rich and freely available.
Eclipse is the standard IDE for the industry, may be because it was made by IBM.
Why I use netbeans
- Netbeans comes pre-installed with many plugins
- Netbeans has a better looking UI than eclipse.
- You hardly need any configuration with netbeans.
But it is on the heavier side as compared to eclipse. You will find most examples on the web using eclipse, expects demos on oracle's site.
It depends on what you are developing.
For example, if you developing a desktop applications. Netbeans comes pre-installed with GUI builder and supports development of java rich internet applcations (javafx, webstart, applet), as it is
developed by Oracle.
On the other hand, for android development, eclipse is the industrial standard. Since google wants you to use eclipse.