I have built many java/grails based web applications in the past 2 years and I would agree that the support for grails/java is much better. The community is pretty active and the fact that grails allows you to fallback to java and runs in a time tested environment(ie the jvm) is an asset in itself. The spring framework which is the backbone for grails is also widely supported and frankly blows RoR out of the water when it comes to documentation, support, experienced developer base.
I would definitely support a grails/Java stack compared to a RoR stack hands down.