I have stayed at both downtown and Research Triangle Marriotts a bunch of times. Never did go to Duke, but seems like Downtown is a little closer. Downtown is a converted Ramada, I think. Even though I was a Platinum, never did see an upgrade at either place. Got on Concierge level consistently at Downtown, seldom at Research Triangle. Always thought Research Triangle location was a little snooty until I got snowed in there for three days about 3 years ago. Never was there on Sunday, but food at both locations restaurants was very acceptable.