I'm looking for a 500GB external drive for data backup. How is WD My Book? Is there a major difference between the older and newer versions besides aesthetics? Also should I spend the extra $ on the higher editions or just stick with essential? I found a 1st gen 500GB essential for $125 and a 2nd gen 160GB essential for $100. also should I just copy my files on the drive for a backup or use a program? thanks for the help!