Thanks for that info.
as far as myself... i have only had one hard drive die on me which i think people referred to as the 'Deathstar' (i.e. IBM Deskstar 40GB) as outside of this i never have had a hard drive fail even though i do have two current hard drives (200GB Seagate IDE/400GB Seagate SATA) that do have some bad blocks on those but seem to work fine at the moment. but i am cautious not to trust those two for anything too important. but outside of that all of my hard drives are still going strong which are...
2.5" = 160GB/160GB/80GB
3.5" = 250GB(WD)/1TB(Samsung)/2TB(Samsung)/2TB(Hitachi)/4TB(Seagate)/5TB(HGST). NOTE: the Hitachi/4TB Seagate/HGST are pretty new though but the others have plenty of age on them as they where running 24/7 for years and the 2TB Samsung still is even though the 250GB(WD)/1TB(Samsung), are semi-retired, as i use them as external backup storage on a USB 3.0 hard drive docking station now as i simply slide them into the docking station and power them up etc.
also, i got a old Maxtor 80GB which i had for ages and that still works (although it's not seen regular usage for years now) and is in a original XBox console right now even though it was in my PC at one point. in another one of my XBox consoles is a 160GB (WD). both IDE. even have a old 80GB Seagate IDE (it's still in use in my old PC) and a 10GB (not sure brand name off the top of my head) in a old Emachines PC. hell, i even kept a ancient 4xxMB Seagate hard drive from my first PC back in 1995 and the hard drive still functions as i used DBAN (Darik's boot and nuke) on it not long ago and that went fine. but it was funny seeing write speed only around 2MB/s on that thing when DBAN was running.
but if i read your post correctly... are you saying Bluray recordable media is the least reliable for you? ; but that's one thing i just never really got into as costs seem to be pretty steep the last i knew and if they don't have CD/DVD reliability that makes them that much less appealing.
as for CD or DVD media... so far i have not had one fail on me. but now that you mentioned it... i am probably going be more careful to run a SHA-1 hash check (using 7-zip) on the burned DATA (against other copies i have) to make sure they match etc. but so far with recordable media... i don't think i have noticed any that degrade to any higher degree especially since i largely stick with Verbatim brand. so i basically agree with you on the 'very reliable' comment on (quality)recordable CD/DVD media) as that's why i still use them but only for files of high importance as it's simply cheaper/more convenient to use hard drives nowadays for general data backup. but come to think of it, i used to have a fair amount of disc scans from years ago so if i scanned those disc years later i would have something to compare to but i don't seem to have those files anymore. still, even running a scan with say Kprobe (i used Kprobe on a Lite-on 1673S mainly) years later should still give us a ball park figure on quality of the disc as i figure if a disc can go 5 years, maybe 10 years, without dropping off much it will probably hold up for our lifetime or close to it and like you say the whole 'read only' is a nice little bonus with recordable CD/DVD as you ain't got to worry about anything getting deleted so as long as you take care of the disc you should be good for a long time to come.
as for SSD's... i only had one of those and it's in my main PC currently which is a Samsung 850 EVO 250GB which i had since May 2015 as that won't die anytime soon (at least as far as failure from writes goes) as it's rated for i think 75TB of writes and at my current rate ill be well over 10 years before i come close to that figure (it seems they will likely go beyond 75TB before actual failure occurs from what i have read). but i waited til the 250GB range SSD's got reasonably priced (and more reliable) before jumping onto the SSD bandwagon. i have heard older SSD's (say 64GB or so types) in general were quite unreliable. still, even though i do believe modern SSD's are more reliable then they once were i still don't trust them for anything important and i also trust regular hard drives more especially after i had a power outage in i think it was May 2016 that corrupted the Windows install on the SSD and, in short, i had to format and start from scratch and it's been fine since. must have been a semi-rare bad luck. but i do know, at least the way i understand it, is that some SSD's have capacitors in them and some do not and it appears my Samsung does not which the ones with capacitors are supposed to be more resistant to data corruption from a power outage as it buys the SSD drive a hair more time to finish any writes it may be doing when the power is pulled etc.
but since you said that involuntary erase can't be revoked on SSD... that's a good point but i think just straight up, at least from what i have heard, when SSD's fail you don't really get any warning where as with hard drives you probably will have some sort of warning before things are totally shot. basically until more time passes (say another 10+ years) and SSD's prove reliable ill take my chances with a regular hard drive over a SSD for trusting anything important on there, especially after i had that, what i would assume was semi-rare, power outage that took out the SSD's data as when i tried to boot windows it was all out of whack (basically could not load up windows). it's the only time i ever had issues because of a power outage as normally it powers back on and all is fine (ill usually play it safe and run a quick error check though to make sure).
p.s. i have had more PSU's fail on me than hard drives. only 1 hard drive died were as i have had 3 PSU's fail. but so far my current PSU in my main PC is the longest lasting one as it's nearly 5 years old as come to think of it, my warranty ends in about a week or two on that but i have faith it will last for a while more because it's Seasonic brand and based on what i read around the time i got them they seem to have one of the lowest failure rates amongst PSU's in general. but the PSU's in the past that did fail on me, failed within about a year of the warranty ending. NOTE: i leave my PC on 24/7 outside of an occasional power down to blow out the dust etc as i try to blow out the dust in my PC at least twice a year or so.