10: Moving parts
In general moving parts are less reliable than solid state, but I'm unconvinced that SSDs are more reliable than HDs.
Against my better judgement, after reading endless descriptions of failures in a 120 GB SSD, I bought one. It was great for about a week. Then one day I faintly smelled that 'roasting electronics smell." My SSD had become a brick with little warning and no chance to recover anything from it.
I've never had that experience with an HD. I've never had one that's life wasn't measured in years and I've never bought another SSD since.