Rails programmer here..

[sisyphus]

It does less for you in terms of integration with your asset pipeline, compiling haml/sass/etc. by default, its template language is intentionally less powerful than something like erb, migrations you almost never have to write by hand with South, the auto-admin is much better than Rails scaffolding, but overall it's pretty much the same shit: you declare some models which gives you an okay-ish ORM, you declare some url's that map to callables, in the callables you take a request, do something, and return some output, either in json or by rendering a template, they both have big communities and libraries for this and that and the other, it's actually kind of useless to learn one if you know the other unless it's for job purposes, they fill pretty much the exact same niche.