Grails vs Rails Productivity Comparison

Many people that using Rails claim that Rails save a lot of effort and increase productivity. With Rails, we can boost "speed of development".

So far many people believe on that statement.

But now there is someone claim Grails is more productive.

AfterThought who wrote this comparison is a consulting company that developers Web applications and distributed systems, is currently doing a project for a Fortune 200 company that was begun on May 30th of 2007. The company did estimates of the amount of effort required to do the project in J2EE, Java/Spring, Rails, and Grails. The numbers they came up with, using a planning tool called Planix (which they have used for several years), looked like this:

In my opinion, this comparison not based on fact. Look at the chart, only Grails is provided actual data, the other just estimate. Its mean they don't try build the same application using Rails. I wondering how they made the estimate.