I'm new to web services and as an introduction I'm playing around with the Twitter API using the Twisted framework in python. I've read up on the different formats they offer, but it's still not clear to me which one I should use in my fairly simple project.
Specifically the practical difference between using JSON or XML is something I'd like guidance on. All I'm doing is requesting the public timeline and caching it locally.
Thanks.
I would say the amount of data being sent over the wire is one factor. XML data stream will be bigger than JSON for the same data. But you can use whatever you know more/have more experience. 
I would recommend JSON, as it's more "pythonic" than XML.
What is the practical difference between xml, json, rss and atom when interfacing with Twitter?