Outer Banks, but it just depends on the weather and what's going on out at sea. It can be glassy and calm or wild and rough either place. Surfers generally prefer the OBX.
The beaches and surf line at Topsail Island is flatter/shallower than it is along the OBX. As such, the under tow, and sometimes the waves, are less a problem at Topsail. All bets are off in either location if weather conditions generate larger surf which in turn creates stronger under tow and rip currents.
We have vacationed in Duck, NC for 30 years in the summer and I'd say 80% of the time neither wave action or under tow were a concern at all.