Hard disk drives
Solid state drives
HDDs have issues with fragmentation, but with good defrag software, that can be remedied. SSDs are horribly expensive, so you'll probably end up with a small-capacity SSD. Until SSDs become more affordable. HDDs are better.
hard drives keep data on them forever. all big government servers with data use hdds
SSDs are ten times faster, consume less power, are less noisy and etc. Hard drives are old technology and will soon become obsolete.
I own an Samsung 850 pro SSD, I love it. The only con is that until this becomes a more common technology the price will stay fairly high for a storage device. It is definitely worth the price now, if you are going to use it to install your OS on it along with a high performance game or two. If you use a lot of storage and don't want to spend large amounts of money consider buying a HHD and a SSD using your SSD for your OS and demanding software and your HHD for all other files.