Probably Murray. That 6-2 6-1 6-4 win over
at the Olympics followed up with a 6-4 6-4 routine win over
(on hard-court) is a changing of the guard in terms of who has the mental edge. And Murray is one of only a handful of players to beat Federer 10 times or more. And Murray would also probably win on clay at this point, since we know how much he has sucked against Djokovic on clay this year (lost 5 straight sets on clay against him).