I found this nice article that shows the evolution of the ASP.Net identity frameworks: http://www.asp.net/identity/overview/getting-started/introduction-to-aspnet-identity
However, I'm interested in how the Windows Identity Framework (WIF) fits into the picture with the new ASP.Net Identity Framework. Are they yet another set of competing Microsoft implementations?
Furthermore, if a developer is interested in supporting SAML authentication (which WIF supports), Active Directory authentication, and Forms Authentication, which would you choose?
ASP.NET Identity is using WIF in the background. WIF is not only WS-Fed, it is now core of .NET framework when it comes to dealing with Principal/Identity. Basically namespace System.IdentityModel is now part of both WIF and .NET 4.5.
Goal of ASP.NET Identity is to provide out-of-the-box authentication mechanism with persistence and some other nifty features and thus replace traditionally used Membership providers which pretty much did the same, on very ugly way (after all, it is over 10 years old).
I personally am never using ASP.NET Identity on the project, but rather do my own user logic when it comes to persistence, mailing etc, and I operate directly with most important WIF classes such as SessionAuthenticationModule, ClaimsAuthenticationManager, ClaimsAuthorizationManager, etc. This gives me ability to write my own custom claims-based abstraction. WIF is all about CBAC (Claims Based Access Control).
Now when it comes to OWIN or not-OWIN, I'd say - go for OWIN (or to be more precise - go for Katana). ASP.NET will be entirely rewritten with new vNext technology, and Katana will play major role there. The sooner you get used to work with Katana middleware, the easier will be transition for you.
Keep in mind that all modules (FormsAuthenticationModule, RoleManagerModule, SessionAuthenticationModule, WSFederationModule,...) are not compatible with OWIN/Katana as concept of ASP.NET extension via IHttpModule is being replaced with Middleware philosophy.
Check out this "hidden" repository where MVC, WebAPI, SignalR are merged into new vNext MVC: