Sakura is faster at that point.
In base form she was able to react and avoid kaguyas chakra arms that naruto and sasuke were struggling to avoid.
She also was able to move obito and herself off of a clip to avoid a nigh instant acid blitz from the dimension, I think she only got burned because she was pouring chakra in him at the time, and because she had to protect him.
Sakura also was pretty fast when she jumped in the air and did her super punch, able to not only punch a jubbi clone away at great speeds but catch it after the fact.
Tsunades speed is tricky, she was keeping up with the raikage ,in v2 , whilst in her byakugou mode. But I'll give it to Sakura because her reflexes seems to be sharper. But then again tsunade is a wreck less fighter because she is a tank.
But logically speaking, Sakura has more control over her chakra , making her able to reach higher speeds that tsunade