The longevity of the 840 pro vs the silent failure of the 840 makes a really good case for the pro.
>The Samsung 840 Series started reporting reallocated sectors after just 100TB, likely because its TLC NAND is more sensitive to voltage-window shrinkage than the MLC flash in the other SSDs. The 840 Series went on to log thousands of reallocated sectors before veering into a ditch on the last stretch before the petabyte threshold. There was no warning before it died, and the SMART attributes said ample spare flash lay in reserve. The SMART stats also showed two batches of uncorrectable errors, one of which hit after only 300TB of writes. Even though the 840 Series technically made it past 900TB, its reliability was compromised long before that.
Note that they seem to be running a sample size of one. To add an anecdote, my own 840 Pro, after relatively little use, died completely and without warning one random day.
Yeah, the random controller failures are really what kills SSDs. This test has been all about proving that wear leveling works and write endurance isn't the thing to be worrying about.
Where did you see that the 840 is still going error-free? It says that the 840 maxed out it's reallocated sectors at around 900TB and veered into a ditch right before the petabyte threshold.
It'd be interesting to run these same tests on enterprise grade drives as well.
Edit: You meant that the 840 Pro is still going, I see.