I would say Nagato, but it would be for more difficult for him considering that his CT is restricted. I think Sage-Mode is normally the best counter for visual powers, but this is not the Byakugan or Sharingan we are talking about... This is the Rinnegan. But nonetheless, Kabuto (Despite 2 of his techniques being restricted) is still extremely versatile and all of his physical capabilities are enhanced tremendously in Sage-Mode. I do not see how Nagato being mobile would crucially matter, as mobile does not equate as fast. It just means you are regularly agile. Kabuto is extremely fast and very agile once in Sage-Mode. But then again, Nagato is a top notch sensor; He would be able to sense where Kabuto is at all times; Thus reacting to it should not be too much of a problem. But Kabuto is a sensor as well, to be fair. I would say Nagato is superior in stamina though. And I do not see Nagato actually blitzing or getting his hands on Kabuto, while Kabuto does not really posses any technique which would pose as high danger to Nagato.