Speed

SSDs does not have any delays contributed by mechanics. There is no mechanical seek, spin-up and rotational latency times. The performance for SSDs can be designed so that the limitation comes from the selected storage interface (example: SATA 1.5 or 3.0Gb). HDDs are limited by the read/write head and media channel which restric the overall sequential performance to 0.5~2Gb/s. Current SDD design is typically 3 to 4 times faster than HDD in terms of read/write speed.

Reliability

Excessive shock is the major cause of failure in both PCs and consumer electronics products. Damage can occur to the heads, disk or even the spindle of the HDD, depending on the magnitude or duration of the shock. NAND-based SSDs are free from the effects of shock and vibration given the lack of moving parts, and are positioned to be the optimal solution for mobile devices. SSDs match the chip mounting and PCB manufacturing reliability of the rest of the system, and the SSD mean time between failure (MTBF) increases significantly over electromechanically based solutions.

Heat and Power

HDD generate more heat and require more power because it needs power to spin up disks and move the heads. In contrast, NAND-based SSDs expend most of their power for the reading or writing of data to/from the NAND or host interface only. The idle and sleep power is minimal. The power used to read or write to/from the NAND device is scalable on performance and capacity, and the SSD can power up and down virtually instantaneously.

Datacenter deployed with SSD requires less air-conditional cooling and electrical power

In mobile devices, extended battery life without sacrificing performance is an important design goal, and can be achieved with SSD.

Noise

SDD is completely silient at zero decibel.

TCO

SSD can be used either to speed up the response time of existing applications as an alternative to buying more servers, or to reduce the number of servers and software licenses deployed

Weight and Form Factor

NAND Flash SSDs is light in weight (5 times lighter than HDD) and deliver smaller form factors in a space constrained UMPC (Ultra Mobile Personal Computer). If it's storage performance you desire, NAND SSDs are currently the fastest natively non-volatile devices you can attach to a storage interface.