Session Login in c# or Cookies Login in c#

1.  Cookies

public ActionResult Login(){

    Response.Cookies["userc"].Value  = log.user_name;

    return RedirectToAction("Index");

}

public ActionResult Logout(){

    Response.Cookies["userc"].Value = "";

    return RedirectToAction("Index");

}

public ActionResult Using(){

    if  (Request.Cookies["userc"] != null && Request.Cookies["userc"].Value != ""){

            string var1 = Request.Cookies["userc"].Value;

    }

    return RedirectToAction("Index");

}

2.  Session

public ActionResult Login(){

    Session["user_id"]  = log.user_name;

    return RedirectToAction("Index");

}

public ActionResult Logout(){

    Session["user_id"] = null;

    return RedirectToAction("Index");

}

public ActionResult Using(){

    if  (Session["user_id"] != null){

            string var1 = Session["user_id"].ToString();

    }

    return RedirectToAction("Index");

}