Even though it is not usually mentioned in the list of features, many manufacturers put more sound-deadening material in their high-end models.
I can tell you that my 2011 Outback Limited is incredibly quiet in the cabin.
I am somebody who is very sensitive to road noise, so–trust me–this is a very quiet vehicle.
However, it is very possible that if you bought the base model or even the mid-level model of the Outback, there might be less sound-deadening material.