>OS X just uses an old NetBSD version similar to OpenBSD's
>NetBSD's is 139MiB/s, FreeBSD, OpenBSD, DragonFlyBSD have very similar code as NetBSD and are probably identical,
It really depends on how fast your memory and processor are.
Everything there was benchmarked with an i7-4790 with DDR3-1600, and very very little running in the background.
Two orders of magnitude difference can't easily be blamed on CPU, in this case it depends on how optimized yes is. I have some older version of coreutils on one machine here and performance is similarly abysmal.
