I am happy with IntelliJ. I'd say use what you generally like for development.
Setting up Openfire for development (in any IDE) is unfortunately still not that easy because of Openfire's messy structure (e.g. dependencies are distributed among four folders and there are 3-4 different folders which need to be added to classpath). You also have to build it with Ant first and pass the "openfireHome" variable to the VM Parameters.