I agree. Sakura is all raw power. Never had incredible speed from what I can recall. She's probably a bit faster than Korra but not enough to make a significant difference.
Everyone talking about sakura seems to be forgetting that she is a shinobi; everyone keeps forgetting that significant training moment during the first 20 episodes of Naruto; kakashi teaches naruto and sasuke about focusing chakra under their feet and explains to them that the skill does more than allow them to stick to objects and walk on water; by pushing off the ground harder than usual, they can move faster and cover greater distances.
We see this when Sasuke sacrifices himself to save naruto. with his average physical abilities he has no way of making it to naruto before haku kills him with his needles; then we see him infusing his legs with chakra and this augmenting his speed and allowing him to make it to naruto before the needles struck.
Chakra infusion is a basic naruto skill that any Chunin, let a lone a Jonin, can perform, which is why they can all walk on water and stick to surfaces with ease. It is the primary reason shinobi in Naruto move so far and fast, precluding special characters with special powers.
Other elements of this battle can be argued; but their is no question about the speed fact. Any chunin level shinobi in the naruto world is at least as fast as Korra at her best or even faster. All competent jonin in Naruto, as a result of their chakra infusing abilities, are faster than someone like Korra. that isn't even a question.
Their is nothing to debate about Sakura being faster than Korra. She is a shinobi. YES, she is faster than Korra, and by a LARGE margin; i don't know if she can blitz Korra. however she is fast enough to avoid anything Korra throws at her, be it fire, water, air, all of it, even lightening which, as we saw in the first Avatar series, isn't quite as fast as normal lightening.