Probably Rafa. He is more dominant at his particular Slam, plus his Slam is next up. What Rafa has done on clay is truly remarkable. I know you don't like to hear that from a *******, but it really is.
No one argues that Rafa is more dominant on this surface and this slam than any other player ever. Take off his clay results and he is mediocre, but including clay, his resume looks like a Top 6 player of all time. Impressive.
Rafa is as likely to win RG 9 times as Fed is to win Wimbledon 8 times.