Ok I have read through the conversations and everyone seems to be focused on who is stronger. Itachi was definitely more experienced and therefore was able to plan out better then his brother but Sasuke had/has a drive that Itachi didn't. That being said there is one major difference no one has really touched on and that seems to be their different fighting styles. I believe Itachi was a much more close combat style where Sasuke likes to have distance. I say this due to the fact that Sasuke developed his lighting style to extend to a pretty good distance and was able to successfully fight deidara. Itachi has only been shown either using genjutsu or hand to hand techniques so I feel that he is a much more close quarter combatant. This would account for the differences in Susanoo's weapons as the bow is greater distance and the sword and shield is for hand to hand.
Just a thought.
Just a thought.