It depends. For anything going into space, especially microsats, the biggest concerns are space, weight, and power. SSDs are better at all of those, plus they don’t have any gyroscopic effects, and they’re much less susceptible to vibrations (e.g. the absolute earthquake at liftoff and the sudden jolts during each rocket stage). They are more susceptible to high-energy particles, but they can be hardened through shielding and parity/redundancy.

For a datacenter on Mars, you’re less concerned with SWaP, only as much as you need to be to get it there as cargo. Obviously that means space and weight are still concerns, but not power.

The other factor with using fewer larger drives is that when you have a failure, you lose a lot more data, and any recovery takes longer.