Who has the longer road back? Ortiz or Khan.

Ortiz for sure.

Khan has been shown up for having poor technique and a weak chin.

Ortiz.... he's quit three times, gave away another fight (against Lamont) and has similar shortcomings to Khan.

Say what you want about Khan, weak chin, cocky, whatever.... he'd never beg his trainer to stop a fight or headbutt an opponent because he was losing and wanted out.