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
There are more options than just SOAP vs JSON. You can do a REST-based protocol (Representational State Transfer) using XML. I think it's easier use than SOAP and you get a much nicer XSD (that you design.) It's rather easy for almost any client to access such services.
On the other hand, JSON parsers are available for almost any language and make it really easy to call from JavaScript if you'll use them via AJAX.
However, SOAP can be rather powerful with tons of standardized extensions that support enterprise features.