It's a bit more nuanced than that. Standard CD-R and DVD-R uses organic dyes for the recording layer, which are sensitive to light and humidity. M-DISC DVD-R used some proprietary inorganic layer, which was more durable in theory and in independent lab tests[1].
When BD-R was introduced, all discs used the same inorganic recording layer, including M-DISC BD-R. That, plus the lack of independent tests, plus the fact that the manufacturer Verbatim likes to muddy the waters between M-DISC DVD-R and BD-R, led some people to conclude that there is nothing special about M-DISC BD-R. However, after a few years, disc manufacturers started making BD-Rs using organic recording layers again with inferior durability[2]. Initially these were marked as "LTH" discs (with the original non-organic BD-Rs marked as "HTL"), but nowadays they mostly stopped marking them at all so you simply don't know what you buy.
With M-DISC BD-R you'll likely get a HTL disc (but it's not garanteed, since they don't advertise it either). Additionally, there's more to durability than the recording layer (such as the material of the reflexive layer, and the overall build quality). And there is at least some anecdotal evidence that M-DISC BD-R are indeed more durable than the median BD-R[3,4].
The consensus among enthusiasts is that for BD-R, M-DISC and Panasonic HTL (Made in Japan) are very good. But they come with a big price premium (about $2 per disc vs $0.60 for some generic LTH disc).
