I think P Cars is better graphically in the attention to detail department but overall I wouldn't say by much, Driveclub is a fantastic looking game!!
Definitely.
On comparative hardware I would say Project Cars paid a lot more attention to detail in terms of crowd, track infrastructure etc. But DC is an amazingly polished game, no doubt about it. The "easily better" is the contentious part. Higher end graphics cards are a different kettle of fish obviously
On console, I doubt Project Cars could ever live up to DriveClub visuals, because it does so much more in terms of physics than DC.
If DC had more circuits than tracks, I would still be playing it now, no question.