I’m stunned that this article exists and was published by Microsoft. Unsafe access to either is clearly undefined behavior. Discussing which one is more or less undefined is like discussing whether it’s safer to run with scissors or a knife: it doesn’t really matter because you’re going to cut yourself badly and possibly in life-changing ways.

Please protect your STL data structures with a mutex. Please keep your thread communications sane. There’s no reason to think through why one is more prone to explosion than another; any conclusions you draw are at best only relevant to your current compiler and STL implementation, and maybe only during some phases of the moon.