well i think that the sharingan is a good eye technique that focuses on genjutsu, and let's u see in more detail that can help with taijutsu, but other than that it's about it...the byakugan it's almost the same, but it specializes in having a more ample space to see improves taijutsu..and let you develop different kind of ninjutsu....so i don't think they are that different...byakugan weakness none, it depends on the user....sharingan weakness-not looking at sharingan (as gai does or zabusa)...i think a byakugan can defeat a sharingan cuz byakugan sees chakra when activated and thus can't be fooled with genjutsu...(when neji or hinata activate their byuakugan all they see is chakra flow and the chakra networks) i think that's why they say that byakugan it's a better eye technique...i wonder if u can upgrade byakugan by stealing someone's byakugan..ahaha
as for the whole sharingan secret....well it keeps on bugging me that pein acts worried about letting madara upgrade his sharingan...maybe after certain upgrades u can conceive Rinnegan??? or awaken as the japanse mythology says izanagi since susanoo amaterasu and tsukuyomi have make their appearnce why not Izanagi...and more than the secrets of the sharingan...wtf is that monster that has the 8 eyes and that revivies when all the kyubi have been captured that is a more intriguing question.
as for the whole sharingan secret....well it keeps on bugging me that pein acts worried about letting madara upgrade his sharingan...maybe after certain upgrades u can conceive Rinnegan??? or awaken as the japanse mythology says izanagi since susanoo amaterasu and tsukuyomi have make their appearnce why not Izanagi...and more than the secrets of the sharingan...wtf is that monster that has the 8 eyes and that revivies when all the kyubi have been captured that is a more intriguing question.