Django is far better thought out, and can be deployed in a very sane manner. A fleet of Mongrels is just an embarrassingly bad way to handle concurrency. "I know, let's write a crappy barely functional web server, spawn a metric ass ton of them, and then balance between them with a proxy. It'll be most leet and super fast! We'll call it a Best Practice. It'll be awesome." In fact, it's fragile, doesn't scale very well, and is complicated to configure. It's also a huge distraction from solving the problem in a sane way--people seem to think "deploying Rails" is solved by this and Capistrano, when really, it's just a new stack of problems.
Otherwise Rails kicks ass, and I like Ruby better than Python (but I'm a perl monger, so I might be brain-damaged into not seeing the beauty of Python). But I do tend to feel like Django is being written by grownups who've got years of development experience, while the Rails folks are making it up as they go along...sometimes going down really poorly chosen paths (I believe Mongrel is an example of this, but I'm no expert).
Then again, I think if I were starting an app from scratch I'd pick Catalyst. But I haven't spent enough time with any of them to know which one is really most productive for the way I work. I think you'll want to try them out, and not take advice from random dudes at news.yc.