Reliability
The issue of reliability is very important because no one wants to lose their data. Here everything is ambiguous for the following reasons.
The hard disk is built on the basis of a magnetic disk, which can stop functioning under the influence of a strong magnetic field or under due to shaking/falling. For example, if you use a laptop with HDD while traveling by car, then due to small shocks, the magnetic disk may be damaged and the data will be damaged or lost, as well as due to such shocks, the wear of the mechanical parts of the disk accelerates and it may fail within 3-5 years.
A solid-state drive assembled from semiconductor chips does not have this kind of problems. Because of its structure, it can be subjected to vibrations or magnetic effects and not be afraid that the data will be lost and the drive is damaged.
However, it also has a disadvantage and it consists in the following – with a sudden power outage, all data may be lost. Since all data is stored on chips, from which information is telegram data read by means of electrical signals, this data can be lost with a sharp loss of electricity.
In terms of reliability, we can say that they have a draw.
Additional items
It is also worth discussing some really important points that may affect your decision in favor of a particular repository.
An important aspect may be the size of the hard disk and solid-state drive. For example, many modern enclosures are designed in such a way that only one hard disk and several SSD drives can be placed in them. This is very convenient because there is more space in the case and air circulation improves if you use a solid-state drive, because it is less massive than a hard drive and does not heat up too much due to the absence of moving parts.
For example, a regular hard drive weighs about 350-700 grams while a solid-state drive weighs about 100 grams. It's all about the mechanical parts in the hard drive and their absence in the SSD.