Graeme has published his 10 reasons to switch from Rails to Grails. I think his case is overstated, but that doesn't mean there aren't some good reasons. To clarify, I have broken his list into three groups: reasons to switch, edge cases, and crap.
1. Reasons to switch from Rails to Grails
These are real issues in Rails applications we have built.
2. Edge Cases
These aren't issues for me, but they are important to some people.
- Mixed source development made easy with the Groovy joint compiler. JRuby is enough for me, but YMMV.
- IntelliJ's JetGroovy Plug-in. I am happy with TextMate for now, but if you are an IDE type check out NetBeans (start with Tor's blog).
- A rich plug-in system that integrates Grails with technologies Java people care about like GWT, DWR, JMS etc. If you think it is hard to build a plugin system you are probably still having flashbacks to your bondage and discipline language.
- Grails 1.0 coming out within the month. Sorry, but "we've never shipped and when we do we'll only be three major releases behind" doesn't motivate me much.
- Built on Spring, the ultimate Enterprise Application Integration technology. In other words, "We have one foot in the past, and leaky abstractions around every corner."
- A buzzing and growing community with a larger traffic mailing list as opposed to a stagnating one. Graeme, I double dare you to say this with a straight face.
- More books coming and being adopted by enterprise. I am a reviewer on some of these books, and they are good. But again, this is "Look--We're second-best and trying hard!" argument.
As a final note: One of the items above rightly deserves to be controversial, and represents the real, enduring difference between Rails and Grails. I think your opinion on that one item should drive most Rails/Grails adoption decisions. Can you spot it?