I would go for the RR Coupe. It is technically not a car to be driven in and is, I think the only exception in the RR world, as it is a Coupe.
Rolls-Royce is the empress of automobiles and as such, it shines over anything else four-wheeled and with a motor that has ever been produced. So, I will go for the RR. The Aston is yet another power-car which is awesome in its own self of course.
Here is a trick: if you bring in a third car to the equation, how does it make you feel about the other two, does it change your opinion? The car is Bugatti Veyron and is currently the fastest production car in the world with its 1001 hp engine.
The Veyron, would personally make me think of upgrading my Aston. However, RR still remains the queen. I would not compare or exchange an RR with anything yet.