I\'m developing a new application for the company. The application have to exchange data from and to iPhone.
Company server side uses .NET framework.
For ex
I would certainly go with JSON, as others already noted - it's faster and data size is smaller. You can also use a data modelling framework like JSONModel to validate the JSON structure, and to autoconvert JSON objects to Obj-C objects.
JSONModel also includes classes for networking and working with APIs - also includes json rpc methods.
Have a look at these links:
Short example of using JSONModel: http://www.touch-code-magazine.com/how-to-make-a-youtube-app-using-mgbox-and-jsonmodel/
Hope these are useful