The Gran Coupe is around 100kg heavier than the equivalent F30 sedan. Are you buying the car more for looks or performance/drivability?
I would say rather look for a low miler F30 with all the bells and whistles and M Sport goodies with lots of Motor Plan left over.
A 320d M Sport - especially the ones with the Shadow performance bits - would be a better buy. If you look hard enough, you might even find some good 330d or 340i models, with a bit higher mileage or with lower spec than the 320d Shadow model.
I cannot rationalise a Gran Coupe purchase over an F30 sedan. The sedan would be lighter, faster, lower cost to insure and would be easier to resell. Gran Coupes don't fly off the used car showrooms.
Also, the Gran Coupes were fully imported, while the F30 sedans were locally made. This means parts availability for the sedan would be better.
If you like the body shape of the Gran Coupe, you may get a better deal on a low miler, previous shape, A5 Sportback with a decent 2.0 TDI or TFSI motor vs a Gran Coupe (whose shape has yet to change). The Sportbacks were generally pre-ordered with S Line kits. This would be an alternative option.
