The main thing is that the flash memory is more durable than the hard drive. Hence, you will be able to use it in more extreme conditions (within reason). Price also? Hard drives store more GB per dollar.
I'm shoping for a new high definition camcorder. Either a sony or canon. I'm good with the camcorder but need help with the terms. What's the difference between an internal hard disk drive (like on the Vixia HG21) and an internal flash memory (like on the Vixia HF10) besides the size of memory (in this case 120GB vs 16GB)? Thanks.