However, SSD is expensive and hose modules with a capacity of 500GB or more can cost almost as much as the entire average computer. The SSDs boast higher performance than the HDDs do, and many computer users are prone to pick an SSD for their PCs ( click here to know the differences among SSD, HDD, and SSHD). #3: Frequency about Adding New Media to Your Computer.#2: Used Storage Space of Your Current Drive.#1: Total Storage Space of Your Current Hard Drive or SSD.