Crucial's RealSSD C300 shows impressive real-life performance in both SATA-II and SATA 6 Gb/s mode. When running on a SATA-II controller it is able to surpass most of the Sandforce based drives, in 6 Gb/s mode it even manages to be the fastest SSD we tested so far. Even though we see a fairly low write speed in our synthetic tests, the real life performance is not hurt significantly by that. Also the improvement from going SATA 6 Gbps is quite small and not worth the added cost for controller or motherboard. In scenarios where the SSD will not gain from the faster speeds of the SATA 6 Gbps interface we also noticed slightly lower performance of the Marvell 6 Gbps controller chip on our ASUS U3S6 card when compared to the Intel ICH10, so that might be an additional point to consider. For the case of the Crucial C300 drive the only improvement SATA 6 Gbps brings is slightly higher read speed. IOPS and write speed are unchanged.
In terms of pricing the Crucial C300 128 GB is also showing excellent numbers. At only $2.10 per GB it is considerably more affordable than the Sandforce drives out there - and delivers equal or higher performance.
The Crucial C300 also packs the much talked-about TRIM feature supported by the latest version of Windows and Linux. The garbage-collecting capabilities of TRIM could become extremely important in the long run, as the drive begins to age. Unlike with magnetic storage devices such as hard drives, where new data can simply be overwritten on top of existing data, for NAND-flash based devices, the portion of the flash chip must be physically erased first, consuming some write cycles. TRIM makes sure that the drive knows immediately when blocks are freed after a file delete which give it a chance to wipe all portions of the flash chips "clean" when the drive is idling, so the cleaned areas are ready to receive new data, faster. Without TRIM, the drive would have to waste those write cycles whenever the OS seeks to write data, which happens to be occupied by deleted data, and that lowers write performance.
Overall the Crucial RealSSD C300 is an awesome drive that looks to be the best consumer SSD on the market right now.