Review here. The 64GB variant of the C300 is a lot slower in write than the bigger sizes, and the Sandforce will be a lot better in write than all the C300s.
As for SATA III, currently there isn't a controller that is better than the standard Intel one for all round performance. Basically you get better sequential but poorer random performance (write). Random performance is more important for OS use, unless you are moving big files round a lot.
Given the good all round performance and added features of the Sandforce controller (Durawrite, RAISE), I would go for the G.Skill at that size, certainly for a boot drive.
Edit: You are on an AMD chipset so you have the best current SATA III controller. It is still marginally slower than the Intel though.
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