Disclaimer: I am the lead programmer for GrailsUI.
I'll give you 3 ways that GrailsUI is superior to RichUI.
1. Managed resources
With GrailsUI, you must specify to the plugin what components you are using within a page, but it will only include the JavaScript and CSS that is required to use the component. If you are using many components, GrailsUI will know only to include your resources one time, and in the correct order. RichUI will include duplicate resources if your components require the same inclusions.
2. Component accessibility
Every YUI component that is created by GrailsUI tags are accessible through their ids elsewhere on the page within the GRAILSUI JavaScript namespace. This means that you can create a data table, and then add a row selection listener to it in your own JavaScript on the page. You have much more control and flexibility because of this.
3. YUI config pass-through
YUI components can be created with many configuration options, so as a GrailsUI user, you can specify these options to the GrailsUI tag and they will be passed through into the underlying YUI component that is created. This allows you great configuration of your components without GrailsUI interfering.
This being said, RichUI is much easier to use, because it provides ways to do the most common things you'll want to do with your widgets. You can do the same things with GrailsUI, but you should know a little more about JavaScript and YUI to take advantage of the most powerful tactics. In general, I think the rule applies that you should
learn the language you are programming.
RichUI also provides more components outside the YUI realm that are useful. I have used both of these UI plugins simultaneously in my projects in the past successfully.
