What are the differences between MLC and SLC SSD drives

AFAIK, Apple's SSD are manufactured by Toshiba, they're no match for high-end aftermarket products such as Intel X-25E, Kingston's E-Series or OCZ Vertex.

SSDs are more reliable and robust than platter hard disk drives as they don't have any moving parts.

The performance of a SSD (even a mediocre one) beats that of the best platter hard disk drives hands down.

And yes, they boost the performance of everything that involves disk operations, even with virtual machines.

All recent consumer drives use MLC flash. Even some enterprise-focused SSDs also use MLC, although with Intel's MLC-HET:

Similar to frequency binning CPUs, the highest quality NAND with the tightest margins gets binned into MLC-HET while everything else is shipped as standard MLC. And just like with frequency binning, there's a good chance you'll get standard MLC that will last a lot longer than it's supposed to. In fact, I've often heard from manufacturers that hitting up to 30K p/e cycles on standard MLC NAND isn't unrealistic. With its MLC-HET Intel also more frequently/thoroughly refreshes idle NAND cells to ensure data integrity over periods of extended use.

So the extra P/E cycles - and therefore increased longevity of the flash memory - come from picking the highest quality NAND chips, as well as adding a significant spare area of 41%.

As for performance, the MLC Intel 710 is generally slightly slower than its older SLC cousin, the X25-E (but the 710 is far cheaper to compensate). Regardless, SandForce MLC drives usually dominate SSD benchmarks due to real-time compression in the controller, rather than depending upon the intrinsic speed of SLC.