Both drives do the same job which is store your personal files such as songs, videos, pictures, documents and applications but they have their own unique differences that are outlined below:
Hard Disk Drives are much cheaper than SDDs as they differ in functionality and many other areas outlined in the subsections below. They will remain cheaper as hard drives use traditional old school technology with a read/write arm. SDD, in comparison, has a bit more sophisticated technology embedded to it, thus they cost more.
The advantage of SSD over HDD in this aspect is as clear as day. It takes most of the devices with SSD just seconds to boot and get up to speed with various operational tasks such as downloading, transferring files or running applications/softwares. In contrast, HDDs are much slower in comparison and will take more time to boot and gain full speed. Even though this might not make a huge difference for an average user, it might just change things around for expert users or small business owners.