Some thoughts on the Padrino and Rails. For the past few weeks, I've been working on a small project that is using Padrino rather than Rails. The interesting thing was that the decision for the technology was based on the idea that the project was only going to have a few objects; at most five or six and as such, didn't need something as large, complex or weighty as Rails. However, something as barebones as Sinatra would not allow for some of the more rapid application development that you get from some of the baked in goodness of Rails - things like Sessions, Flash, Form helpers and generators all speed up development fairly considerably. With that in mind, Padrino was the framework of choice.
Now Padrino is interesting. It's a great little framework, but, the temptation is to look at it's relative light-weightedness in comparison to Rails and think it will require less learning time or up-front knowledge for someone with little experience of the framework or of something like Rails. This is really a false economy. I would, in fact, say that for a beginner, Rails, not Padrino, is the sensible choice. Rails has excellent documentation right out of the gate, Padrino - well the documentation is just okay. It's enough for a seasoned developer to use, but unless you are already familiar with Rails, you might find yourself floundering a bit trying to figure out how to do something relatively simple.
The other area in which Rails really excells is in the sensible defaults - Padrino, in a way, requires you to really know your technology up front. Padrino is less opinionated than Rails and allows you to plug in various different components to pretty much any part of the system, even coding your own if you fancy. However, this kind of flexibility comes at a price - you need to know what you're going to use up front - Datamapper? ActiveRecord? Sequel? With Rails, the decision has been made for you - ActiveRecord. No faffing about with analysis paralysis. On the other hand, this kind of agnostic framework is good for those with specific requirements to use the non-defaults.
Where Padrino really shines in my opinion, is in the admin support. Generating an admin backend to your app is so simple. Granted with Rails you can use ActiveAdmin or something, but really, having this kind of CRUD baked in to a framework is awesome - one of the things, incidentally, that I love about Django.
So, when should you use Padrino? Well, my advice is, when you already know Rails and you want a framework that's a little bit smaller. But, heed this will if you are new to Ruby based web frameworks - learn Rails first.