No such ones that would make one of them unsuitable for some task that another copes with.

What the hell??

They evolve differently. Saying *BSD is like 4.4BSD is still developed by ucb to provide a single base for all BSD.

Michael W Lucas wrote in Absolute FreeBSD (3rd):

Absolute BSD (No Starch Press, 2002) was my first technology book and was written when the various BSD operating system had more in common than they wanted to admit. The second edition, Absolute FreeBSD (No Starch Press, 2007), came out after the BSDs had diverged, and detailed FreeBSD’s advances in the previous five year