Congrats on getting into both schools! Being familiar with the area, both schools are really good, and I'm not really sure if I would say that Duke is more "established" ... if anything, if you are intending to stay in the research-triangle area, both schools are going to carry some serious weight. Even if you plan on getting a job further north in the DC-beltway, you are again in a toss-up between the two, unless there is a specific sub-field that you are attempting to target, such as robotics, systems, graphics, etc. Plus the further north you go, you're going to run into a lot more people graduating from other schools in the mid-Atlantic and northeast such as MD, NY, NJ, PE, MA, etc. If you are planning on an academic route, I unfortunately can't help you there :-(
BTW, I'm not attempting to hi-jack the original question, but while we're on this topic, is there a de-facto resource for finding the rankings of graduate CS programs in the computer graphics speciality? For instance USNWR's speciality rankings do not include the graphics sub-category, yet I've seen Universities claim to be some X rank in the field. For instance, you mentioned that UNC is the top computer graphics program in the U.S., yet I would have thought that distinction would have gone to Stanford, considering the plethora of computer-graphics research that has been generated by them in the last five-to-ten years.
As far as a ranking generated from a school's research in the sub-domain of computer graphics for the last five years, the closest thing I could find is this:
http://academic.rese...5&continentid=2
Is there any other resource that is considered a more precise indicator of a graduate program's performance in the computer graphics specialty?