Let's say that this is going to be Misaki from the beginning of the main series and Lelouche from before the Black Knights betrayed him.
Round 1: Fist fight, no powers
Round 2: Both characters are in a mix of Academy City and whatever city Ashford Academy is located in; they are each trying to safely capture the others (though in Misaki's case, she's after Zero rather than Lelouche). Assume that the Zero helmet can provide immunity to Shokuho's telepathy unless she's within range of his Geass.
Now, this is interesting...
Round 1: Goes to Lelouch because Misaki is so weak in NT and Railgun it becomes a running joke.
Round 2: Misaki can win with the proximity that she is actually more intelligent than Lelouch can ever hope (Level 5, in general, has intelligence equal to Super Computer stated in NT and Railgun). But Lelouch is more strategic and might be more strategic in war tactics than Kumokawa Seria that up to now we can only measure tactical thinking of Shokuhou... But, Mental Out is more dangerous than Geass so I still lean toward Misaki.
Round 1: Both pass out from exhaustion of throwing the first punch
Round 2: Both are about equal in strategy but Mental Out lets Misaki control much more people and in a much greater range than the Geass that requires contact.
[video]https://m.youtube.com/watch?v=Aw4F0saf2wo[/video]
not to mention her own already existing clique. Going to say she captures Lelouch faster than he can her