Fed is
1. Grass
2. Fast HC
3. Slow HC
4. Clay
That goes from fastest to slowest, actually.
Nadal is difficult because after Clay, it's hard to say...it's probably fast HC, but he had an extended great grass run with 2 Wimbys before falling off, and slow HC he's always been competitive, just had some bad luck at AO relative to perhaps some good luck at USO. I do believe fast HC, as long as it's not blazing fast, might actually suit him a bit better than slow HC, as his ball has more action as long as the bounce is still reasonably high.
To me Novak is the most interesting, because he appears to excel on slower courts, but clearly isn't as good on clay, which is even slower than slow HC. Probably due to the different movement on clay, and how it rewards spinnier shots. Even with Nadal in the picture, I think it's clear Novak's level is way higher on slow hc... then as courts get faster, he can struggle, but on the fastest courts of all, grass courts...he's done quite well. You can argue the grass is "slow", but it's still faster than the US. It's possible that the serve and return is rewarded more on grass than fast hc's, and the difference in speed isn't enough to outweigh that or help Novak relatively on fast hc's. In that same vein, many of the faster outdoor hards have some pop and action with a decent height bounce. This isn't ideal for Novak, who probably leans toward preferring slow and low courts. Look at indoor performance...
