I mentioned RoR, because that was what I've used in my previous project.
RoR's learning curve is much more higher than Tornado. I don't even think that is fair to compare those two.
IMHO, RoR is more suitable for apps that requires lots of objects, views, etc.. E.g: A business app or a website.
In our case, we don't have that many tables, but lots of code around it and our app also runs on top of a single page. All the rest is taken care via AJAX.
One more factor in our decision was simplicity. You can easily dive into Tornado's code ( web.py ) and understand, whereas in RoR you need to read a lot of code, and Ruby is also making it harder to find out the flow of the code with its advanced concepts ( was called extends I believe )
And I am not a big fan of Active Record as well. We use PyMongo to communicate directly with MongoDb.
Tornado's Asynchronous abilities also an advantage.
Also I did not have that much of experience to use RoR in full scale, and if I got stuck on something, I need to read a lot and I don't like that.
