For me it is a tough question. I think the reasons for picking one over the other have to do with time in the saddle, after the final fitting, and configuration of parts.
Although the De Rosa is my favorite ride, the Pinarello is used more often.
The pin was recently converted from a double to a triple. It is more supportive of helping me get up the hills until I get back in shape. It will be converted further from an 8V to 9V with a 26t instead of a 23. It also changes at the other end from 12 to 13. This bike will help me with hills and getting back to a performance level I can enjoy more.
P1050226 on Flickr
The De Rosa is a 10v with the rear block from 11-25 but has a 53/39 chain set comparted to the Pin with 52/42/30. The other difference is clinchers on the Pin and tubulars on the DR.
P1040764 on Flickr
Frame size is different too, Pin 57.5, DR 59.1
The bike that was a revelation of good riding was the Colnago Supperissimo. Little did i understand that it is a bit small. I would still rank it up there for best ride (tubulars)
IMG_20180707_074628 on Flickr