Although flash based hard drives are becoming more popular, they still don't have the same value for money that current hard drives achieve. For same price as a 32 GB non-volatile flash disk you can get a whopping 750 GB hard drive. For the meantime you can take advantage of a combination of these two technologies.

Hybrid hard drives, or H-HDD combine these two technologies to offer an increase in performance as well as an improvement in power consumption. The flash memory is stored onboard the hard drive and picks up where a normal hard drive leaves off. You can get much higher speed as the mechanical latency associated with most hard drive is not there. Power consumption can be improved because frequently used application data can be stored and then pulled from the flash memory.

These advantages apply mostly to notebook hard drives. Laptop drives are much slower than desktop hard drives, and power drain is a big concern. With these additions H-HDD manufacturers hope to make laptop hard drives reach similar speeds to their desktop counterparts.

Currently, hybrid hard drives require that you run Windows Vista, not because it needs Vista, but because it needs ReadyDrive, a feature that comes with Vista. Which data is stored on the flash part of the drive is controlled by the operating system, and in Vista, ReadyDrive takes care of this. ReadyDrive sees how you use your programs and which ones you use the most, it then puts the most heavily accessed application data onto the flash memory part of the hard drive.

Power is saved when there is a read/write done onto the flash portion of the disk. Because there is no motor, flash media draws much less power. However, when the data is written to the disk the motor still needs to be used and therefore uses that power that was saved.

The super-fast access speeds of the flash disk more than make up for the lower transfer rates that is able to maintain. The fast cache that has become an integral part of hard drives is not replace in these models, but the flash part just complements the functions of the drive.

In actual use there is not really much advantage to this kind of hard drive. Despite some hype, there is very noticeable difference in real world applications and doesn't save much power either. Just wait for flash-only drives to come down in price, which is already happening, or for now just use a traditional model.