Why upgrade to solid state hard drive on desktop computer

Why upgrade to a solid state hard drive on desktop computer if non-solid state hard drive speed = 6GB/s and solid state hard drive speed = 6GB/s

Will I just be paying more to get less space? they both claim to have the same speed. I know SSD will use less power, make no sound and will be harder to damage if you drop them. But if I plan on placing a hard drive on a desktop computer why should I consider using a SSD?

The storage subsystem consists of a (large) number of technologies which together perform the IO tasks of the computer. These technologies are linked together, and the speed of the system is determined by the slowest link in the chain: the bottleneck. The 6Gbps SATA speed you see mentioned there is the measurement of one part of this chain, the drive's external interface. But not the slowest part. Neither solid state drives nor hard drives can actually saturate the interface. Solid state drives do come a lot closer to saturating the interface link in the chain than hard drives do. The performance difference between the slowest links in the chain for hard drives and solid state drives is huge.

Here are some benchmarks of my hard drive and SSD. You can see a quite big difference. This first one is of my hard drive:

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CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
                           Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

           Sequential Read :   109.284 MB/s
          Sequential Write :   106.174 MB/s
         Random Read 512KB :    36.481 MB/s
        Random Write 512KB :    56.847 MB/s
    Random Read 4KB (QD=1) :     0.440 MB/s [   107.5 IOPS]
   Random Write 4KB (QD=1) :     1.091 MB/s [   266.4 IOPS]
   Random Read 4KB (QD=32) :     0.636 MB/s [   155.2 IOPS]
  Random Write 4KB (QD=32) :     1.085 MB/s [   264.8 IOPS]

  Test : 1000 MB [F: 88.4% (69.1/78.1 GB)] (x5)
  Date : 2012/07/26 16:57:47
    OS : Windows 7 Ultimate Edition SP1 [6.1 Build 7601] (x64)

And this one is of my SSD:

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
                           Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

           Sequential Read :   266.271 MB/s
          Sequential Write :   192.082 MB/s
         Random Read 512KB :   182.861 MB/s
        Random Write 512KB :   184.971 MB/s
    Random Read 4KB (QD=1) :    22.632 MB/s [  5525.5 IOPS]
   Random Write 4KB (QD=1) :    46.049 MB/s [ 11242.5 IOPS]
   Random Read 4KB (QD=32) :   139.447 MB/s [ 34044.6 IOPS]
  Random Write 4KB (QD=32) :    71.849 MB/s [ 17541.2 IOPS]

  Test : 1000 MB [K: 88.0% (160.0/181.8 GB)] (x5)
  Date : 2012/07/26 17:04:38
    OS : Windows 7 Ultimate Edition SP1 [6.1 Build 7601] (x64)

Both of these have the same SATA 3Gbps interface. Despite that you can see quite significant differences in measured performance, specially in Random Read 4KB (QD=32).

You may also want to switch to SSD if big number IOPS is what you desire. For SSD -> http://en.wikipedia.org/wiki/IOPS

For Spin drives it considerably less.

It's meaningful for some - depends on what you are doing on the PC.