How much portable hard drive capacity you need depends on the size of your computer's internal hard drive and whether you want to back up all or some of your files. If you plan to regularly back up your entire computer system, the portable hard drive capacity should at least match that of your primary computer. Beyond that, experts don't say much about the pros and cons of a larger versus a smaller drive because on this matter, at least, practicality trumps all. Users with tons of data to back up are advised to choose an appropriately sized external hard drive; currently, portable hard drive capacity maxes out at 4TB (terabytes). Most consumers, however, will find that an external hard drive with 320GB (gigabytes) or 500GB is more than sufficient.
A chart detailing portable hard drive capacity of devices produced by Seagate notes that a 500GB drive can hold up to 160,000 photos, 8,330 hours of music, 500 hours of digital video, and 125 DVD-quality movies. That's a lot of data storage for a typical household. The Hitachi Touro Mobile Pro is available in two sizes 500GB and 750GB. With the price difference between the two just $10 to $15, the 750GB version offers the better deal for shoppers. This external hard drive also includes 3GB of free online storage, something you won't find in most cheap hard drives.
The other models we researched feature 500GB of portable hard drive capacity. A review on Best Buy reports the Seagate FreeAgent GoFlex Ultra holds a trove of large photos taken during travels that are now instantly accessible. The Buffalo MiniStation Stealth likewise offers the right combination of portable hard drive capacity and speed, according to comments posted on Amazon, but just in case you're concerned about running out of space, you can bump up to the 1TB version for just $35 more. The Western Digital My Passport Essential gets a thumbs-up from consumers posting reviews at Newegg, where they laud the combination of small physical size with generous portable hard drive capacity.
For some frugal consumers, cost per gigabyte is a related consideration. The 750GB Hitachi Touro Mobile Pro, for example, starts at 13 cents per gigabyte, while the 500GB Buffalo MiniStation Stealth goes for about 16 cents per gigabyte. The per gigabyte cost of the other 500GB portable hard drives we researched ranges between 16 and 20 cents.
Larger external hard drives often boast lower per gigabyte costs even though the total cost propels you out of cheap territory. The 1TB Hewlett Packard HP Portable, for example, costs approximately 15 cents per gigabyte and retails for about $150. The mammoth Seagate 4TB GoFlex Desk drive sells for $279, for a per gigabyte cost of only 7 cents.