A rank Temari Fuuton VS B rank Sasuke/Itachi katon

[Icelerate]

Rank means nothing in relation to power; rank only tells you how hard a jutsu is to learn.
Further, an elemental jutsu can always beat the element it is meant to beat regardless of rank. In other words the Uchiha's C-Ranked Katon will beat even an S-Ranked Fuuton. Though Naruto's FRS was S-Ranked, Yamato still said to watch out for Sasuke's Katon.

I disagree with your opinion and there are people who think that FRS will beat amaterasu even though I disagree with that notion as well. I am more of a middle man and think that a jutsu with equal power will be decided on the element advantage. On the other hand, if one jutsu is stronger than the other, it doesn't matter what element they are but that the stronger jutsu will win.

Also Yamato only told Naruto to watch out because Sasuke may have had developed an S rank fire tech himself which he now has (amaterasu).