My setup is somewhat similar to John's in concept. My O/S is on an SSD. Most, but not all, Trainz installs are on another separate 1TB SSD. But the core of my activities, content creation and the like, are on a fast HDD because I trust them more than a SDD. And I back up anything important to a mirrored LAN HDD system (Synology).
Yes, a decent SSD may be faster but do I trust it - hmm, no!
Similar however I still have 11 year old OCZ Agility 3s in service, a 120GB which is a boot drive on my oldest PC and 2 240TGB ones that have TS12 on one and Mint Linux on the other, I'm inclined to trust SSDs or rather certain makes of them. Curiously they are all showing 100% Performance and health in Hard Disk Sentinel and have been showing more than 100 days life left for years..... go figure.
Number 2 PC has 4 SSDs, 240GB boot and for Trainz 1 x 240GB, 1 x 500GB plus 2 x 2TB and 1 x 4TB spinners, I do have an add on PCIe 6 port SATA 3 controller in it though, main PC has again 4 SSDs, a 240GB for the OS, 2 x 1TB and 1 x 500GB plus 2 x 2TB spinners.
I also have installs on Spinners and the main difference is speed of database repairs and loading, when Trainz is up and running there isn't really any vast difference in performance. Important stuff like content creation is on spinners backed up and mirrored also on both my main PCs.
I have 2 mirrored 4 TB backups for OS Images Data and Trainz and another 4TB that has copies of everything I have ever downloaded, that's Trainz assets, installers and all program installers as well, I've actually networked them by sharing through one of my PCs as my Seagate NAS box ( bad choice) won't work without SMB1 and required logging into to Seagate every time I wanted to use it, I stripped the drives out of it and reused them. This system also works for backing up my Linux Install,the backup drives are switched off when not being used.
I use Macrium reflect for system drive images and FreeFileSync for backing up Trainz and my Content Creation stuff, it's pretty fast as it just syncs / mirrors the backups with the original, to restore just reverse the direction.
I would never ever trust the cloud as being a permanent storage, been bitten once so never again besides at 20MB/s upload it would take for ever to backup all my stuff.