Are you kidding? Sorry but if you cast your mind back the sharingan did have some uses before MS besides genjutsu. Of course it still matters, their speeds being equal has nothing to do with it. Sasuke will be able to see every attack coming, how is that not a huge advantage?
And let's make something clear; Sasuke is far more versatile than BS. He has clones, ninja weapons, multiple variants of chidori, a range of fire jutsu, substitutions (which exploding tags can be attached to) and kirin. BS will be attacking head on, whereas Sasuke could do that, go for deception or use his techniques as a setup for Kirin, which is an insta win if he pulls it off.
B*S would also be able to see all of Sasuke's attacks coming its not an advantage! speed is equal remember (even if you can see it in advance you can only move as fast as your body will allow, B*S has greater reactions than Sasuke as well).
Clone, ninja weapons, substitutions B*S can do them too.
Black Star does not have to attack head on, he has mid and long range attack too.
Black Star has good sensing abilities and also has the 6th Sense, Soul Perception.
So Sasuke clones would be easily seen though, since Sasuke cannot perform the shadow clone. Kirin requires a lot of prep which aint gonna happen in this fight TBH, in the manga it required a large coverage of Amataratsu spread and several fire jutsu shot into the sky, to change the atmosphere and create a 'Natural' storm.
B*S can keep firing shadow swords and and shadow scarf from range if he likes, they are easily capable of cutting Sasuke in two.