We tried both for the first time in 2009 and loved both.
We went back to both in 2010 and I'll be honest with you, we were disappointed with WPC. The service was poor and the desserts seem pre-packaged where we had really enjoyed them the year before.
On the other hand, RR did not disappoint. The service and food were excellent. People complain about the dumbing down of menus in recent years with the DP but this is not the case with RR which has a huge selection of tempting dishes. The bread pudding for dessert is our second favourite dessert at WDW behind the bread pudding at 'Ohana.