Employers used to look for developers familiar with a specific IDE because each IDE had their own way of writing build/deploy scripts (for j2ee applications). That's usually not the case anymore (for new projects) because a lot of projects are built with Maven using its own build files. Both IDEs support Maven, so which IDE you pick is gradually turning into a personal choice, woo!
I prefer Netbeans, but Eclipse has been extremely popular with employers as you can see in this graph:
I've no idea why it got the popularity it did, for me Netbeans just does everything better and looks prettier.