I'm not sure why so many guys are placing Ferrer as a sort of #3 clay player in the world and suddenly nobody is talking about Fed. I'm pretty sure that Fed would blow Ferrer off the court. btw, I'm saying this with all respect to Ferrer and his fans.
I prefer Fed to Ferrer and would like you to be right here, but:
a) Fed plays bad this year, while Ferrer seems to continue his hot 2012 form
b) Clay is a natural environment for David, while it can't be said about Roger
c) Roger won't play as much clay, while Ferrer will play a lot more and with his incredible consistensy it means much. He'll probably reach SF o even F in Monte Carlo in which Fed won't even compete.
Unless they both land in the same part of the draw, Ferrer will probably achieve more on clay.