In ASP.NET MVC 3, which is more correct to use: Json() or new JsonResult()? Either returns the same result. Thanks for helping solve an office debate.
Json() is just an extension method that actually returns a JsonResult object behind the scenes (rather than needing to call the constructor directly).
I almost always use the Extension Method myself. This keeps more in line with the other common return types from Action Methods like View(), PartialView(), etc.
I also make sure to create an extension method for any custom ActionResult types that I create. In the end it's a matter of personal preference.