New features in MVC versions (MVC 3 vs. MVC 4 vs. MVC 5)

ASP.NET MVC 3

• New Project Templates having support for HTML 5 and CSS 3.
• Improved Model validation.
• Razor View Engine introduced with a bundle of new features.
• Having support for Multiple View Engines i.e. Web Forms view engine, Razor or open source.
• Controller improvements like ViewBag property and ActionResults Types etc.
• Unobtrusive JavaScript approach.
• Improved Dependency Injection with new IDependencyResolver.
• Partial page output caching.

ASP.NET MVC 4

• ASP.NET Web API, a framework that simplifies the creation of HTTP services and serving a wide range of clients.
• Adaptive rendering and other look-n-feel improvements to Default Project Templates.
• A truly Empty Project Template.
• Based on jQuery Mobile, new Mobile Project Template introduced.
• Support for adding controller to other project folders also.
• Task Support for Asynchronous Controllers.
• Controlling Bundling and Minification through web.config.
• Support for OAuth and OpenID logins using DotNetOpenAuth library.
• Support for Windows Azure SDK 1.6 and new releases.

ASP.NET MVC 5

• Bootstrap replaced the default MVC template.
• ASP.NET Identity for authentication and identity management.
• Authentication Filters for authenticating user by custom or third-party authentication provider.
• With the help of Filter overrides, we can now override filters on a method or controller.
• Attribute Routing is now integrated into MVC 5.

Source: http://www.webdevelopmenthelp.net/2014/02/ASP.NET-MVC3-Vs-MVC4-Vs-MVC5.html