[BinaryPie]

I would use whatever seems to suit best for your task at hand.

Need to build a site quickly that is mostly information based such as a blog or some kind of editorial site. I'd choose python with django. The automatic admin section is great for this type of task.

Need to build something with a lot of popular features (twitter, mash ups, simple shopping carts, etc..) and don't have time to really learn every little detail. Ruby using Rails might be a good solution as there are thousands of demo and live applications out there to borrow from. Should reduce your development time.

If you are looking for a new hobby language. I would choose python as it doesn't have quite as large or fanatic following as ruby. It also has a lot of room for growth. There are many libraries and verticals in the python market which could use some help.

End of the day though. It's up to you and the problem you are solving.