That red 64KB curve shows how bad Sandforce is at compressing data. Anvil found that "Compressing a 1GB testfile using 7z (normal) results in a ~1.73MB file", which is an incredible 578x compression factor. And yet Sandforce evidently could not compress it at all, since it took about a 50% performance hit compared to the blue curve.

My guess is that a lot of data on most people's SSD will be similarly hard for Sandforce to compress.