SSD. Had to replace my SSD just this weekend as it just suddenly died on me.
Should have taken it as a warning since I lost all my data on it about 2 months ago and had to put it in a different PC to format it and reload Windows.
Worst thing is that when I did a health check on it minutes before it betrayed me, it said the health was sitting at 97%.
SSD as primary HDD and larger spindle HDD in caddy in optical bay of laptop for storage... cannot imagine life without OS/apps installed and running on SSD, 4 seconds boot to desktop is expected by me now.
Everything has been replaced with enterprise-class SSDs because I am tired of hard drives, especially Seagate 2TB ones that have a high failure rate, I am slowly replacing everything with SSD, including drives in the NAS