Trying to recap: the only thing I am interested in is the lifespan. And that is also the one thing many manufacturers are reluctant to tell - more about that below.
There are generally two different kinds of SSD available: consumer use and datacenter use. Datacenter use is twice the price (or more). These may have better power failure protection, and may have better sustained-write behaviour.
On the consumer side the sustained-write behaviour is crappy: the device will read data at full speed for a second or two, and then it will stall a while for housekeeping.
So, as this is probably all the same crap, lets focus on the lifespan. And lets normalize all values to the number of PE-cycles. There are currently three different quality bands (plus a forth):
- 180-350 cycles, QLC
- 220-400 cycles, TLC
- 500-800 cycles, TLC
And all of them cost nearly the same.
The fourth band is somewhere around 1250 cycles, which is the same as datacenter/mostly-read, i.e. 0.7 DWPD over 5 years. And these cost usually twice as much.
If I remember correctly, both of the Crucial (BX and MX) belong to band 2.
In band 3 we have, among others, the HP S700, Verbatim Vi550, Lexar NS100, Samsung 860EVO, and certain Seagate Barracuda (but not the barracuda Q). In band 4 is e.g. Seagate IronWolf or Samsung 860PRO. (These are NOT recommendations, I didn't test them all.)
How to derive the normalized PE-cycles: for the more professional devices there may be a DWPD value, then you have to figure out the warranty-timespan, and multiply the DWPD with the number of days. For others there may be a TBW value, then divide this by the capacity. But beware: often the TBW value is not given for the actual device, but for the biggest-capacity device in the series!
But often nothing at all is given. Then there is still a way, because manufacturers do obviousely consider their customers stupid, but they themselves are not stupid when it comes to the money. So, look for the warranty specs. The warranty specs usually point to some fine-print exclusions - another document. These exclusions may then mention a limit of TBW, and point to some value given in the product specs.
In the case of Crucial, a few months ago when I checked this, there was a link to Full Specifications, but no such value given. And I went searching around in circles and couldn`t find the mentioned product specs document. Finally with google I did find the document. On the webpage it was practically impossible to find.
Now checking again, they have fixed that. The value is now in the Specifications, and also my local reseller shows it on their product page. (If that were there earlier, I would not have bothered to search the website.)
Anyway, that search adventure left an impression, so I for my part wouldn't buy that brand.