RAID 1, also known as mirroring, involves having at least two hard drives, where the data is written identically to both drives. This provides a high level of redundancy, as if one drive fails, the other still has a complete copy of the data. In my experience, RAID 1 is often used in scenarios where data protection is a higher priority than performance or storage space efficiency.
On the other hand, RAID 5 uses a technique called striping with parity. It requires at least three hard drives, and data is written across the drives in small blocks, while also storing parity information. If a single drive fails, the lost data can be reconstructed using the parity information from the remaining drives. RAID 5 provides a balance between data redundancy, storage space efficiency, and performance. I've found that RAID 5 is a popular choice for organizations that need a good balance of data protection and performance, without sacrificing too much storage space.