Nalan probably has some pretty serious moves. In the prologue to Words of Radiance, Jasnah overhears a herald saying to Nale that they (he and Nale) shouldn't have let Szeth keep the honorblade. Here's a link to another post where I quoted that passage. By saying they shouldn't have let him keep it, Ishar/Kalak (whoever that other herald is) is implying that he and Nalan have the ability to take it away from Szeth. And Szeth, as we all know, is a complete badchull.
However, Adolin is more than just a good duelist. He is a fantastic duelist. He's one of the best. In any fair duel, he is not going to be beaten down in a matter of minutes. Then again, I don't think that Darkness would constrain himself to a fair duel against anyone, unless he was compelled by law.
Szeth beat Adolin because of surprise and surges. Adolin didn't know how to deal with a surgebinder. Now he knows that they exist, and will be training to be prepared against them.
Nalan used to be using the law to justify the execution of proto-radiants. He was confined by the law, but he didn't really care about upholding it. It was just a tool, or an obstacle. Now he seems to have a great interest in making sure justice comes to the leadership of Shinovar. The same leadership that just happens to possess most of the honorblades.
At the same time, now that Szeth has "died", the Stone Shamans are supposed to retrieve Jezrien's honorblade. Once Nale is done with Shinovar, he will probably be heading for Urithiru. There's an honorblade there, and multiple proto-radiants. And if the Stone Shaman Honorblade Retrieval Team wants to get Jezrien's honorblade back, they would be wise to bring at least one honorblade with them.
Maybe, just maybe, we will see a fight that includes the Stone Shaman Elite, the Kholins, and the Skybreakers. Multiple honorblades. Surgebinding. Madness.
If Nalan comes for Adolin's father, I suspect there will be far too much happening for us to see a direct comparison of Adolin and Nalan's dueling skills. They may match blades, but it won't be just them.