That's a tough call. When you're a fan/former student who grew up in NC, it's hard to argue otherwise. However, in my case, UNC/NCSU was a bigger rivalry. Maybe it was the time and the location. There weren't many dook fans in rural eastern NC. At my school, you were "Carolina" or "State." In my hometown, church, you name it. For me, the dook rivalry never really took a hold until after K became successful. By that time, I was out of school and living in Myrtle Beach. But, over the last 30 years, it's become the biggest rivalry.
I will add that, when I lived in Charlotte, I was living with a girl who was from Ohio and her dad was a former OSU cheerleader (in the mid-60s). We all went to a game in Columbus (OSU/Michigan) one November, around 1998. I've never seen football fans that crazy... ever.