Theoretically, more cache and higher speed of rotation improve HD performance. SATA 3 is common and SATA 6 is just out. It should provide some improvements over SATA 3. SCSI seems to still take the prize with platter type devices. Solid state HDs didn't offer much (if any) improvement over platter types initially but are gaining ground. All I know is what I read and all I told is only what I've read so take it with a grain of salt.
Can a bigger size hard drive, e.g.-2tb 16mb cache, & cache make an operating system,e.g.-windows xp, boot-up & multi-task faster? In-other words, make a system's O.S. more efficiently faster? What other specs make a h.d. faster?