I think that the title pretty much sums it up:
What's the difference between RouteLink() and ActionLink() in ASP.NET MVC?
RouteLink()
ActionLink()
i.e. when do you use Html.RouteLink() and when do you use Html.ActionLink() in your View?
Html.RouteLink()
Html.ActionLink()
In addition to the other answers given here, RouteLink is a little bit faster, and cannot ever match the wrong route because you changed your routing table.