From my experience, SSDs are more prone to failure and have limited writes. They are ment for running the OS, databases for fast access, and games / apps. They are not ment for long time storage and frequent overwrites, like movies, which usually means download, delete and repeat which wears the memory quickly. One uses electric current to short memory cells and switch them from 0 to 1 and viceversa, the other uses a magnetic layer which supports a lot more overwrites on the same bit.
If keeping important data on them, I would use them only in a redundant RAID configuration and/or with frequent backups so I wouldn’t cry if one of them fails. And when they fail, there are no recovery options as with HDDs (even if very expensive, at least you have a chance).
I also wouldn’t touch used server SSDs, their lifetime is already shortened from the start. I had 3 Intel, enterprise-grade SSD changes in our company servers, each after about 3 years - they just wear out. For consumer / home SSDs the typical lifetime is 5 years, but that takes into account minor / “normal” usage, ie. if used as OS disks. And maybe power users could extend that with moving the swap/pagefile and temporary files (ie browser cache, logs, etc) on a spinning disk, but it defeats the purpose of having an SSD for speed in the first place.
If you have media (like movies) in mind, you’ll find sooner than later that you’ll need more space, and with HDDs the price per GB is lower than SSDs.
If you have no issue with 1. noise, 2. speed (any HDD is fast enough for movie playback and are decent for download), 3. concurrent access, or 4. physical shocks from transport, go with HDDs, even used ones.