There's a big omission in Carlo's post and that is the no. of weeks/years Fed's spent at no.1 vis a vis Nadal. In short, we could say that Fed is the more consistent and dominant player across all surfaces and through the length of his career. Peak for peak, Nadal has had his measure on clay for sure and arguably on grass and HC as well. However, since Nadal fans feel obliged to add the disclaimer that Nadal in 2017 is not playing at the same level as he used to (and neither is Fed for that matter but we'll leave that be for the time being), it has to be pointed out that Fed fans could validly make the same argument about Wimbledon 2008 and AO 2009. Yes, Fed was much closer to his peak then than Nadal in 2017 but it wasn't a peak for peak match up. Wimbledon 2007 is where they squared off peak for peak and Fed edged a close five setter. Had there been less of an age gap between the two, we could have had more matches with both in their peak to see who bests who peak for peak on grass and HC. But of this I am sure, even peak Fed would not be able to beat peak Nadal on those surfaces as convincingly as peak Nadal beat peak Fed on clay. Nadal's domination on clay is more absolute (by far) than Fed's on his favourite surfaces. It's just that by the time he got good enough to get to Fed on grass and HC, Fed had started to slide from his peak save the W 2007 match. Unlike Borg, though, Fed didn't run away from Nadal and even beat Djokovic at RG in arguably his career best year to get to Nadal for a familiar result. And it has eventually paid off as he has demonstrated astonishing longevity in staying with Nadal and even beating him at this late stage of his career which was an unexpected result for most of us.