Some would argue that it's hardcourt since clay and grass are both natural surfaces and grass has slowed down over the years. Grass is the surface in which Nadal has had to make the least adjusment from clay in his career. It took longer for Nadal to truly excel on hardcourt as opposed to grass so I say hardcourt is the most different. Maybe in the 80's and 90's the grass would have been the case, not anymore. Anyway, I still find it preposterous that you think it's surprising that Nadal would be the favorite at Wimby in which he will be defending his title and he's been at least a 3 time finalist. If say Murray were odds on favorite I would be surprised, mainly because he's done nothing at slams outside of one up to this point. Another one would be making Nadal the favorite at the US Open. He never won that or made a final, so then your statement would hold up better. But Wimby? C'mon man, you're just putting Nadal down a notch. If Joker or Murray were favorites I'd be surprised, but not Nadal. He's proven himself.