Check this link:
Feature Comparison - Json.NET, DataContractJsonSerializer & JavaScriptSerializer
It has a good feature comparision between Json.NET, DataContractJsonSerializer & JavaScriptSerializer. Just have a look at it & then decide which one to use based on your requirement.
Also, check this:
ASP.NET MVC 4 & Json.NET :
We (.Net Team) now use and support the popular Json.NET serializer for
handling of JSON data. Json.NET is the default JSON serializer
used by ASP.NET Web API and it includes support for data contracts,
anonymous types, dynamic types, Dates, TimeSpans, object reference
preservation, indenting, camel casing and many other useful
serialization features.