Hard drives are not really any better than any other method.
A hdd can still get wiped/corrupted by virus/os crash/whatever while plugged in. Can get damaged by a surge while plugged in. Can be easily damaged by a drop while being carried or unplugged. Can fail whe stored in one of those firesafes from the heat.
The best method if to never rely on one type of media. Copy data to another hard disk and burn dvd's as well.