how can you even not see that , itachi is waaay better than sasuke .. itachi is a better ninja than sasuke coz he did all that for his village , and he kept protecting his village ,, He did all that without even complaining while sasuke left and he's a hatter .
also itachi is way stronger than sasuke , sasuke didnt defeat itachi but itachi had to let sasuke kill him . he said that to naruto when he said " there's something i have to do "
Itachi! Even though Itachi was seriously sick to the point he could die, they've proven that he could have easily beaten sasuke...But he was trying to get sasuke on the right path again by letting sasuke kill him. Even until the end of his life, the only thing that mattered to him was sasuke.
So to answer:
Who's better power-wise: Itachi(His fight with sasuke, he was greatly ill, who knows how powerful he would have been at full health.) ;
Who's better and has kinder soul: Itachi(He let everyone believe he was so horrible, and killed all of his clan because the village made him, and continued on to better look out and strengthen sasuke. Everything he did was for sasuke...He is a true brother, person, and ninja
This is just my opinion, but I believe it's Itachi. He continued to fool Sasuke even after his death until *spoilers* Madara/Tobi/Obito tells him. That spurs his whole "need to destroy Konoha" thing. Itachi graduated way earlier than Sasuke and was an amazing prodigy. Plus his heart was incorruptible and he was always loyal to Konoha even when he joined the Akatsuki. Sasuke on the other hand became consumed by revenge and hate. Plus he's kinda whiney.
In all honesty when it comes to power, if we went with how sasuke is now then it would be sasuke, Just because he has picked up a lot, also because you know he's the main character.
But if we went with sasuke when he actually fuaght Itachi then it would have been Itachi (If not for the fact that Itachi handed that battle over) All in all at one point or another they both were better than each other so it pretty equal. :)