Murray by far, Nadal's "Si" is much worse than his vamos.
Nadal is not as nearly in your face annoying as Murray. He dosn't pump fists in opponent's FACE like Murray. He usually turns his back to his opponent or is not even looking at him. Murray on the other hand does it deliberately in opponent's face. He did it to Gasquet last year at Wimbledon and Gasquet even complained about it.
Can't wait till someone does it to him.
But then again Murray's got ugliness on his side, so it only makes sense that he gets his face in opponent's mind. That nightmare doesn't end until way after you've been defeated by the ugly monster. That's the reason why he's doing so well at the moment. He has learned to utilise his strength, his extreme ugliness.