If you ask me and I'm certainly not the authority on this but here goes.
Most SSDs regardless of who makes it or what model it is will have a 4K Random Read Speed Benchmark of at least 30 MB/s. 4K Random is the number that most closely mirrors that of every day storage device usage. That is, grabbing little seemingly random chunks of data from all over the drive such as when you boot Windows or load programs. Compare that to a hard drive, a 2TB Western Digital Black Edition which is usually one of the best performing hard drives on the market, its 4K Random numbers is a measly .50 MB/s (yes, you read right, half a megabyte per second!).
Now you can see how upgrading to an SSD can and will make your machine take off like a rocket.