I work in data recovery and I'm always being asked what kind of backup device my customers should use. The fact is, there are a lot of choices and a lot of different situations with different answers.
Whatever device you choose for backup, remember the most important part of backing up is to always have more than one copy. Your backup device does you little good if it holds the only copy of your files.
USB Flash drives:
Most Inexpensive Easy to damage
Easiest to Transport Easy to Lose
High Compatibility Difficult to recover
Fast copy speeds
External Hard Drives:
Inexpensive Some are bulky
Higher Capacity Greater damage if dropped
Easy to transport Can be expensive to recover
High Compatibility Some require external power
Faster Copy Speeds
Easier to recover
Secondary Hard drive(internal)
Inexpensive Not optional on most laptops
Higher Capacity Not optional on all Desktops
Fully compatible Can fail simultaneously
Fastest Copy Speeds Does not protect data if PC Stolen
Easy to Recover Requires some knowledge to install
Less risk of damage
NAS Box or Small Server
Higher Capacity Higher Cost
Redundancy is Optional Requires more knowledge to setup
Accessible to all PC's
on your network at once
Fast Copy Speeds
Low risk of damage
Compatible with most PC
RAID5 NAS or Server
Highest Capacity Highest Cost
Highest Redundancy Requires most knowledge to Setup
Fastest Copy Times Requires specialized equipment or software
Accessible to all PC's Most expensive to recover if failed
on your network at once
Ability to survive single
drive failures without
Now, armed with that short list of options, let's help you decide which option best suits you. If you move around a lot, you go to school, work out of the office or travel for work a USB flash drive is often the simplest form of backup and allows you to move data between home, office or school without lugging a large drive around. we recommend these as a part of most peoples backup solution. Next you will want a more stable form of backup(harder to damage).
For your tougher backup device you will have to decided what kind of budget you have, how much data will need to be backed up and how often. If you have a great deal of data from several computers in your home or office you will likely want to use a NAS box or setup extra drive(s) in one of your existing desktops to use as a server. If you only have one or two computers or the budget just won't cover a RAID or NAS solutions you can simply purchase an external USB or eSATA hard drive, usually less than $100. This can be moved between computers and used for backing up.
Now remember to Sync your data. This means anything you update or create while away that is saved on your USB flash needs to be copied into your computer and your computer needs to be backed up onto the external drive or server.
For more information on backing up, verifying backups and different types of backup devices, visit my blog at http://www.aitsavemyfiles.com/armor-itrecoveryblog.php
or search through the other tips available here on FixYa.