nadal is the better player on grass than federer? who are you kidding.... federer has won 6 wimbledons! nadal only 2! they've only played 3 times on grass, with federer having a 2-1 edge (unlike them getting to play the majority of their matches on nadals' best surface, in fact more than half of their matches, how is that fair to federer?!)
and the only reason nadal is even winning any wimbledon's nowadays is because the wimbledon committee have made their grass courts play like a slower hard court with a bit of grass topping for cosmetic purposes! plus their use of heavy balls to insure long rallies and a "true bounce" the grass courts of theirs no more plays like "real" grass courts than a volleyball is like a baseball!
this was all due to the displeasure of the game of the 70's and 80's when fans complained that matches were not fun to watch basically because of all the serve and volleyers and the two shot points ( serve, volley, end) so they impleted these changes to make the game more pleasing to watch, however, now they have gone the other end of the spectrum too much...
if they had the grass courts of back in the day like grass courts used to really be like with it being super fast, super low bounces, skidding, weird bounces, dead parts of the courts, etcetera there is NO WAY ON THIS PLANET THAT NADAL WOULD EVER WIN WIMBLEDON! and that is the truth!
nadal would be lucky to get thru to the finals playing on the grass of the 50's, 60's, 70's and 80's playing all the great serve and volleyers of that era who knew how to serve and volley i might add unlike NO ONE in the top of todays' game.... of course, nadal would be helped by today's technology if he was able to use the rackets he uses now. nadal is the prime example of someone totally helped by todays' racket technology! the way he hits his forehand, and he grips the racket? no way on this planet if you gave him a wood racket or a old school graphite racket would his balls ever go in the court, they would be flying out of the stadium! but due to the super over powerful rackets of today,and the strings, the racekts of today are basically "trampolines" thus making nadal able to hit that severe spin and topspin thus making it hard to play him because of that reason!
federer and all the other players still hit more traditional strokes and grips, thus they COULD play and be at the top if you gave them a wood racket or less powerful metal/graphite racket...