And let's not forget the motherboard, in this discussion.

Win 7 often reports that the drives are the slowest component of a system, when in fact, it is the northbridge or southbridge chips that are relatively slow. (The northbridge chip typically controls the RAM and the graphics card, AND the southbridge chip. The southbridge chip, among other things, controls the disk drives.)  Sometimes, a motherboard uses relatively cheap condensors, also impairing the speed.

No sense in putting SSD's on a mediocre motherboard.