In The Decameron by Boccaccio, the relevant social differences seem to be that (1)  Ricciardo was know to Caterina's father and beloved by them whereas Guiscardo was unknown and a complete surprise to Ghismonda's father, and that (2) while Ricciardo was of comparable birth and station, Guiscardo was of lowly humble birth and therefore beneath Ghismonda's station, thus her father's lineage and family line would be weakened.

The happy ending that Ricciardo and Caterina experience, a wedding to make their union legitimate, was what they desired in the first place and was only gained after mush pleading and reasoning. Ghismonda didn't pursue permission to marry but instead begged that she be allowed to die with Guiscardo. So in a perverse way, even Guiscardo and Ghismonda got their desires.