I think he's a better (or more successful, if you want it to be more objective, I suppose) volleyer than Federer at the moment (Fed's somewhat declined in this... and Rafa seems to be playing his best net game ever in the last few months).
In terms of their entire careers, Fed has been a better volleyer, but who knows how much improvement Rafa has left in his volley game.
Rafa's definitely a talented volleyer and you could tell this from even his earliest days. What he's learnt is to better utilize his natural volleying talent and develop a game around it.
It's definitely not as "pretty" as Federer, but Nadal does have a knack to create the illusion that he's an elite volleyer because he rarely seems to be in a bad situation at the net - whereas Federer takes his chances.
It's just a difference in styles.
In Fed's absolute peak, though, he was a destroyer of worlds at the net - but I wouldn't characterize his career, overall, as one of the all-time volleying greats (same goes for Nadal).
Fedal's bread and butter is baseline tennis, at the end of the day.