Objective reasons for using Python or Ruby for a new REST Web API
I would say the important thing is that regardless of which you choose, make sure that your choice does not leak through your REST API.  It should not matter to the client of your API which you chose.
So this thread is definitely NOT a thread for why Python is better than Ruby or the inverse. Instead, this thread is for objective criticism on why you would pick one over the other to write a RESTful web API that's going to be used by many different clients, (mobile, web browsers, tablets etc).
Again, don't compare Ruby on Rails vs Django. This isn't a web app that's dependent on high level frameworks such as RoR or Django. I'd just like to hear why someone might choose one over the other to write a RESTful web API that they had to start tomorrow, completely from scratch and reasons they might go from one to another.
For me, syntax and language features are completely superfluous. The both offer an abundant amount of features and certainly both can achieve the same exact end goals. I think if someone flips a coin, it's a good enough reason to use one over the other. I'd just love to see what some of you web service experts who are very passionate about their work respond to why they would use one over the other in a very objective format.