I came here looking to research the Byakugan (and what better community for Hyuuga-related ideas is there?). I'm actually trying to figure out how the Sharingan and Byakugan respond to genjutsu so that I can improve a scene inside of my own fan fic.
See, the Sharingan notices details, while the Byakugan sees through things (and if you like the anime, acts like a magnifying lens). So, Sasuke would detect an illusion, perhaps, by noticing that tall grass is actually short glass, as he might notice the genjutsu flickering in places. While Neji might notice, via X-Ray, that part of the grass is transparent.
However, while Sasuke can see the color of chakra, Neji can't see through Shadow Clones with even amounts - however, he does pick up on the real Naruto taking cover. So to me, Sasuke has the more "notice an immediate effect" whereas Neji might notice a physical discrepancy.
There are scenes of the Sharingan breaking genjutsu that I can work off of, but there aren't nearly as many examples of the Byakugan breaking genjutsu.
For instance; I'd be interested to know what would happen if Ino used her Mind Transfer jutsu on Neji or Hinata from behind (giggity), without them being aware.
Would they detect the jutsu and call her on it, aware that she tried to mindjack them? There's evidence that Sakura was not conscious of Ino's attempts until the preliminary round of the Chunin Exams. However, Obito dispelled Ino's control, likely due to having a Sharingan.
So, in short: How does the Byakugan respond/detect to genjutsu/control techniques?
Rather than make another thread, I'll roll this question in here too:
Can the Sharingan copy the Gentle Fist?
Some would say yes, as I would, since it copied Rock Lee's style. However, I believe the disadvantages demonstrated with Sasuke copying Lee's style would similarly apply to Neji's as well. There was a discussion I read recently about the vectoring involved, and while I barely made heads or tails of it, I can see how copying an instance of Neji or Hinata would prove disasterous, were a Sharingan user to opt for Gentle Fist during a fight.
Or in short, while I think he could copy some of the movements, would Sasuke be able to duplicate the Gentle Fist effectively, or would it suffer from his body's lack of training similar to how it did with Rock Lee's techniques?