Whereas most 2.5" portable hard drives employ magnetic hard disks with moving parts that can easily break, flash drives are much more durable thanks to their solid state nature, having been known to survive drops of 6' or more on a routine basis and can even survive a load or three in the laundry. A flash drive is also much easier to pocket than a portable hard drive and can attached to a lanyard or keychain, plus they can be significantly less expensive if only a basic model is needed.