...Your comparison between Edberg and Nadal are based on his stats when he used to play with the technology and courts available to him (not to mention what used to be considered standard for physical requirements back then) compared to what Rafa has now.. That is completely unfair and almost like apples and oranges.
E: Might be cliche or sound like a broken record, but I sincerely do not think there is anyone who has some sense or logic believes that a prime Sampras couldn't pick up some titles with the conditions in today's game. As successful as he was in the 90s? Maybe not, but being able to pick up slam titles, that is definite. I mean seriously, just watch how he came into the net compared to how players these days do. The players these days are sitting ducks and have no clue compared to Sampras on how to position themselves, which is heavily the reason why they get passed.
Since we are talking about current conditions and why players don´t attack the net like they used to, it´s totally relevant to compare Nadal and Edberg using todays conditions.It is a bit unfair to Edberg, sure, but that´s the whole point. Todays conditions are unfair to attacking players, and that´s why we don´t see them anymore.
As for Sampras, he relied on his serve more than anything. In his prime his serve was almost unbreakable on fast surfaces. He was a great volleyer, but his serve was the key that set him up at the net. Slower surfaces on the current era would take away much of that advantage, and they would make it difficult for him to hit a winning first volley. On top of that, his groundstrokes would be badly exposed, especially his backhand. Can you honestly imagine Sampras breaking Djokovic´s or Nadal´s serve on a slow hard court? Or even being able to attack the net? I doubt it.