That’s true, but it’s not a glaring difference. Duke won in 2001. Roy won in 05 with Doh’s guys and then he had Hansbrough for 4 years when they won in 09. Duke then won it in 2010 and 2015, Roy won in 2017. Since then both teams have been up and down. Both have missed the tournament (you guys don’t get out of the technicality of 2020). I’d say they’re pretty similar.
They're similar, but Carolina has been better. That 2001 title for Duke was before Roy returned to Carolina. It also falls outside your last 20 year timeframe, BTW. Carolina has more national championships in the last 20 years. They're both elite programs, but Carolina has had the slight edge since Roy Williams returned to Carolina.