I am planning to develop an REST based services for one of my client who is very touchy about performance related issues. Any thoughts on the comparison between normal REST using servlets & REST with Rails. I have created one service (add/update/delete/list) in Ruby on Rails using a tutorial. But that wasn't that efficient as compared to normal normal REST using servlets.
I haven't seen or run any benchmarks on RESTful applications specifically, but I'm willing to go out on a limb and say that Rails will probably be slower than a well-written set of servlets. For my purposes, this difference has been insignificant, but obviously your mileage may vary.
The real benefits of building RESTful systems in Rails lie more on the developer side - Rails makes it easy to follow most of the RESTful principles, and its features and conventions mean that more of your time and energy is devoted to the interesting problems of building your service, rather than to the nitty-gritty of handling browser-unsupported HTTP verbs and the like. In my experience, it's just faster and more enjoyable to develop with Ruby, Rails, and REST than in other languages and frameworks.