<p>Itachi low-diff </p>

<p>I'd say Itachi. Chiyo's statement comes to mind. "When fighting the sharingan, 1 on 1, abandon the field..." So Shik-deezy should try to create a distraction and bounce. He can't win. Even with Shikamaru's 200+ IQ, Itachi was also regarded as a genius, on Hokage-level intelligence at I believe 8 years old. So Shikamaru isn't gonna have enough of an intelligence advantage to make up for Itachi's fighting advantage. More than half of the reason Itachi is so dangerous is the element of surprise factor of his techniques and overall style, and Shikamaru of all people is going to greatly mitigate that advantage with full knowledge. He won't fall for 3 tomoe genjutsu off the bat, can break finger genjutsu by having by breaking his own finger ironically enough, and his shadows actually pack some serious raw power and range now. The expanding shadow Shikadai used has a surprise factor of it's own that could secure Shikamaru's victory. </p><p>Itachi still has a far greater advantage considering his own genius intellect and his superior ability when it come to one on one fighting, but it's not like Shikamaru's odds of victory are at zero. Itachi is strong in that department himself and it's going to take more than just brains to defeat a man of Itachi's caliber. There's not much of a terrain advantage to either of them here either. </p><p>I'm going to go with Itachi simply because Shikamaru is very limited when it comes to ninjutsu, bukijutsu, and has no better counter to genjutsu anyhow. It's hard to think up of a way how he can win, because even with full knowledge he doesn't have the skillset to counter Itachi's skillset. Hinata and Shino don't have much to their skillset either. </p>