If your app has a lot of non-user facing CRUD (i.e. a CMS or publishing app), Django offers some incredible shortcuts with the built-in admin app.
I also think Python is a better systems programming language (i.e. calling out to unix during web stuff), due to it's scientific background.
Otherwise RoR and Django are roughly the same MVC frameworks -- opinionated conventions about models with a database abstraction layer, and views and controllers (templates and views in Django terms).
Likewise, Ruby and Python are roughly the same -- object oriented scripting languages.
But for your specific questions, I'd say Rails wins by a long shot. There are a lot more Rails companies/jobs in the Bay area (though more Python than Ruby jobs, again because of science). Rails 3 shows the community is still going strong.
Sinatra is the most fun for simple web services and it integrates with Rails no problem.
And most importantly, you can use Heroku for Ruby deployment, which is an incredible short cut for launching a site and its impossible to go back to being a sys-admin once you realize it's not necessary.