The Gran Coupe is undeniably a beautiful car, and I think it is the best execution of the 4-door coupe concept. I was very impressed with the exterior and the presence of the car when I was looking at the one at my dealership. The Nevada interior and lack of Nappa dash/contrast stitching, however, made for a very disappointing interior in a car with a sticker price of $104k.
While the GC is a looker, I still prefer the looks of the coupe if aesthetics are the most important factor. For me, that was the case as I don't need a practical car at this point in my life. I agree that the sloping roofline, slimmer window, and longer doors give the car the classic, luxury coupe look. I think the door sills on the coupe look nicer (more substantial) than the Gran Coupe. I know there's not too much you can do about that as you are obviously going to have narrower openings with 4 doors instead of 2, but they looked a bit dinky on the GC, particularly in the back. Not a big deal by any means (hard to find legit "problems" with cars at this level), and it's only noticeable when you compare side-by-side. I'm nit picking here, but just little things I noticed.