I think healthy DelPo is more likely winner than healthy Ferrer in their matches. Lets take a look at their matches:
I don't what happened in their first match in AO'08, DelPo retired there. '08 's-Hertogenbosh SF was thus their first match which was finished. Ferrer won. And I'd say that happened because Ferrer is better on grass. But then their next two matches showed DelPo-in-form can beat Ferrer, especially on hardcourts. But then DelPo injured, and hasn't been at his best, still he was able to fight until the fifth set in DC final, played on Ferru's best surface, clay. And maybe this year's Miami match was also too early for DelPo, he hadn't found his best level. And their last meeting was at SW19, and Ferrer won again, and I think that happened because he's a better grass court player. So, I'd say their corrected H2H would be 2-2, DelPo: Tokyo & Miami '09, Ferru: 's-Hert. & Wimby.
So, I think those 2008 Tokyo and 2009 Miami wins prove peak DelPo is better than Ferrer. But I'd say that there are surfaces where Ferrer is better. DelPo hasn't been too impressive on grass, and I think that may be because of his height and low bounce of grass. I remember reading somewhere Olympic tennis had shorter grass, that made the court faster and higher-bouncing, that may be the reason why he played so well on Olympic grass. And while height is problem when hitting to low bounce, Ferrer definitely doesn't have that problem, and that's why Ferrer is a better grass player than DelPo. Clay and slow HCs are another surfaces where Ferrer has a good chance against DelPo, even if DelPo is a good clay courter, clay and slow HCs enable Ferrer to win matches by grinding. Still, peak DelPo should have an advantage over Ferru on slow surfaces. But fast HCs are where DelPo is just too good against Ferrer. Fast HCs reward offensive playing, and unlike on grass, the bounce is enough high fro DelPo.
So, if we have peak DelPo playing peak Ferrer, then I'd say DelPo is absolute favourite on fast HCs, and favourite also on slow HCs and clay, even if Ferru has a chance there. But grass in another case, DelPo must improve his grass play or otherwise Ferru routines him on grass.
Edit: and to the poll's question, if Ferru beats DelPo twice in a row on fast HCs, and DelPo doesn't have injury problems and hasn't beaten Ferru on other surfaces, then I'll say Ferru owns DelPo.