Yes, I’m under the impression that your original write up is exactly backwards...
SSD is bigger and more reliable. Not so susceptible to being bumped and corrupted. Longer lasting, fewer moving parts.
HDD is faster, but less reliable and shorter life because of moving parts. Most people put their boot files and OS on the HDD for faster start, but they save all data to the SSD.
Do I have it backwards?
You have it backwards. . . The only reason for using a spinning platter drive anymore is cost of larger storage capacity is cheaper. . . and that is usually used in server applications in RAID arrays where a failed drive can be hot swapped out live without losing any data because the data is mirrored on other drives for safety. It wont be too much longer before even that advantage will be lost, because servers don’t typically do much data writing, which is what wears out NAND SSD memory drives. . . and the cost reduction of high capacity of NAND chips and the reduction of energy to operate them is so much lower than running and cooling spinning drives, that alone will eventually doom mechanical HDD storage.
TSMC is building a chip foundry in Arizona that will be producing ICs that can use 5 nanometer traces. Samsung’s just started using 7 nanometer. That can drop the chip power consumption down considerably. TSMC is Apple’s primary IC maker for their Apple designed A13 SoC (System on a Chip) processors that drive their iPhones and iPads which benchmark better than some of the latest laptop Intel i5 chips at higher power consumptions!. . . In fact, better and faster than the intel i5 Apple itself puts in their entry level MacBook Pro!
Course I would give similar advice for a mechanical HDD also. I learned many moons ago to backup C: as soon as you get installed with all drivers and programs. If your data changes every day, think about what you simply must have to figure out what to backup and when. Programs don't need to be backed up, just the data it produces. On some programs I actually backup the data to separate multiple locations. I write my Bible studies in Word but save the study to at least 2 separate places to keep from typing 6-8 pages per chapter over again. My Genesis study alone lasted 57 weeks. If I lost it, I would literally loose thousands of pages. I also have hundreds of gigs of video's of my home study groups. I use a 6TB drive as my main backup and a 2 TB as a second backup.