Ask HN: Rails or Sinatra?

Hey, experienced ruby devs. Which ruby framework is best, in terms of flexibility and scalability? I have a background in PHP. I know the basics of Ruby but, I am still learning. Thanks.

Padrino is pretty good, but really, the docs are lacking in my opinion. For someone new to coding ruby on the web, getting a good grounding with Rails and then using Padrino is, in my opinion, a better idea.