Adam,
GVR is built on a sandy loam, while Riverdale I believe is on clay/clay loam. That makes a lot of difference in playability. In fact, during construction there was debate at GVR about whether to leave the fairway bunkers as native soil because it was so sandy. Luckily, though, the decision was made to add drainage and bring in sand, as the loam in the soil retained quite a bit of moisture after rain events.