Padrino extends Sinatra with a wealth of extra features: namespaced route aliases, nested routes, controllers, i18n / internationalization, mailer system, django-esque admin interface and unified logging.
Most of these features can be added to Sinatra already, either manually or by selecting from a wide assortment of independent plugins. Padrino, on the other hand, provides a standard suite of functionality that, hopefully, will continue to be improved as a whole over time. It feels a lot like Ramaze (http://ramaze.net/) but with the similar functionality wrapped around Sinatra instead.
Most of these features can be added to Sinatra already, either manually or by selecting from a wide assortment of independent plugins. Padrino, on the other hand, provides a standard suite of functionality that, hopefully, will continue to be improved as a whole over time. It feels a lot like Ramaze (http://ramaze.net/) but with the similar functionality wrapped around Sinatra instead.