@deathinvenice
Itachi isn't the strongest just yet
he need the other Mangekyou Sharingan to be able to claim that position in the first place
the senju clan were some people who lived in some forest and together with Madara they built the future village of Konohagakure
so you could say Naruto is their descendant but the clan didn't really have something special about them(it's the same as,for example,the celtic tribes in Europe long ago)
the Mangekyou Sharingan seems to have only two forms - the one of Itachi and Madaras brother and the one Madara has(and Sasuke(or he will))
since Kakashi isn't a member of that clan his eye looks different
if there's someone who didn't notice that then he propably didn't really read or cared to read the chapter
it still does matter if he gets Sasukes eyes with or without the Mangekyou
because if Itachi gets Sasukes eyes and Sasuke still doesn't have the Mangekyou by then then Itachi would still loose his light someday
you do get greater power if you have two pairs of the Sharingan but you are only able to withstand the lost of your sight when you have two MANGEKYOU Sharingans
________________