Check the guarantee
Do not buy any disk drive product that does not include at least a 3 year guarantee. If the maker is not confident that the drive will last that long why should you be ? With external drives make sure that includes the power supply brick as those are prone to failure as well.
Do some math .. Divide cost by length of guarantee and see what cost per year you will paying. If it comes out to be more than on-line storage think again.