It's not clear how much better than they are than regular media since there haven't been many tests. There are two that I'm aware of, one by the French Archives (who've done this a few times it so happens) and one by the US DoD.

The French found that M-DISC didn't perform much better than regular DVDs and that a weird kind of glass DVD beat everything else hands down.

The Americans found no errors at all in their tests of M-DISC while all other disks encountered them.

I suspect the important differences were:

- The Americans' tested the discs after light exposure, the French did not. It may be that the light caused the regular DVDs to fail but not the M-DISC.

- The French tests were far longer (1000h) than the Americans' (24h). It may be that M-DISC can't survive the adverse conditions past a certain point that the Americans didn't reach.

Also as far as I'm aware, there are no tests of the Blu-Ray variant of M-DISC.

Personally, given the cost of M-DISC, I'd buy a few cheap terrible Blu-Rays instead and just make sure they're not exposed to too much light.

French test: https://documents.lne.fr/publications/guides-documents-techn...

American: http://www.esystor.com/images/China_Lake_Full_Report.pdf

> While the exact properties of M-DISC are a trade secret

If long-term accessibility is the goal, not off to a good start...