SLC stands for “single level cell.” MLC stands for “Multi-level cell.” SLC is faster than MLC. However, MLC allows more data to be stored than SLC. When the capacity of an SSD increases, you want to pay particular attention to weather the manufacturer has gone to MLC. ALL Memoright and MTRON SSDs sold by DV Nation are SLC…EVEN the 2.5″ 128GB Memoright! This means there is NO performance penalty. Toshiba and others have announced MLC SSDs that are spec’d to read at an admirable 100MB/s, but we think that even if they achieve that, their IOPS performance will likely be lower than SLC. But these MLC SSDs are currently WRITING at half the speed of SLC. So, to sum it up, SLC will always give TOP performance, but if you want to get into SSDs, you might save a little money on MLC SSDs.