Re: Who are the Clay court specialists?
As for the Delpo + Berdych vs Ferrer debates, take their results at Monte Carlo, Rome, Madrid & Roland Garros from the past 2 years to make a comparison (ignoring 250s and 500s because it takes up too much time and it would inspire fewer quips of "vulture"):
2011 Monte Carlo:
Berdych beats Rochus, loses to Ljubicic in 3rd Round
Ferrer beats F. Lopez, Raonic, Troicki and Melzer, loses to Nadal in final
Del Potro beats Starace and Cilic, withdraws before playing Nadal in third round
Berdych beats Granollers and Monaco, loses to Bellucci in quarter finals
Ferrer beats Mannarino and Stakhovsky, loses to Djokovic in quarter finals
Berdych beats Monaco and Nieminen, loses to Gasquet in quarter finals.
2011 French Open:
Berdych loses to Robert in first round
Del Potro beats Karlovic and Kavcic, loses to Djokovic in third round
Ferrer beats Nieminen, Benneteau and Stakhovsky, loses to Monfils in fourth round
2012 Monte Carlo:
Ferrer loses to Bellucci in second round
Berdych beats Cilic, Nishikori and Murray, loses to Djokovic in semi finals
Ferrer beats Stepanek and Almagro, loses to Federer in quarter finals
Del Potro beats Mayer, Youzhny, Cilic and Dolgopolov, loses to Berdych in semi finals
Berdych beats Anderson, Monfils, Verdasco, Del Potro, loses to Federer in final
Del Potro beats Llodra and Youzhny, loses to Tsonga in third round
Ferrer beats Verdasco, Simon and Gasquet, loses to Nadal in semi finals
Berdych beats Kubot and Almagro, loses to Nadal in quarter finals
2012 French Open:
Berdych beats Sela, Llodra and Anderson, loses to Del Potro in fourth round
Del Potro beats Montanes, Roger-Vasselin, Cilic and Berdych, loses to Federer in quarter finals
Ferrer beats Lacko, Paire, Youzhny, Granollers and Almagro, loses to Nadal in semi finals
In the past couple years Berdych and Del Potro have beaten each other once, and Ferrer beat Del Potro in the Davis Cup final, Berdych and Ferrer haven't played each other on clay for several years.
Make of that what you will.