Others may argue, but I feel it is best on a number of grounds to limit SSD to your system and applications, and put your data on an HDD.
One reason is cost. Data tends to consume most of the storage capacity on any computer, and more so as the computer grows more, ummm, mature. You can get 8 TB of HDD storage for less than the cost of a 1 TB SSD.
A second reason is the lifespan of the drive. Although no longer anywhere nearly as severe a problem as it was in the early days of SSDs, they still have limited write cycles. Your O/S and applications are often read but very seldom written to, but your data is written all the time with every saved file.
A third reason is basic efficiency. Your data reading and storage do not require the speed of an SSD -- the slower data transfer speeds of an HDD are just fine for most data and you do not notice any difference in performance. Furthermore, even with a computer HEAVILY laden with many large applications suites and whatnot, a 256 GB SSD is generally more than adequate.
Now, the downside of this is the different way these two drives fail. SSDs tend to monitor their own health and fail only gradually, permitting you to save their contents and replace the drive before they utterly fail. HDDs tend to fail catastrophically without warning, and if you don't have your data backed up it might be VERY expensive even to partially retrieve it. But the Mean Time Between Failure (MTBF) of most HDDs these days is EXTREMELY long -- it is highly likely you will be getting a new computer LONG before one fails. But it is a good idea to back up your data frequently anyway.