Way back when OpenSolaris was around, I put it on a server to experiment with. There was a lot to like about it, but one thing I didn't like was there was a lot of obvious cruft that has built up over the years. Things were in places that I didn't expect, but they had been there since 1904 when people wrote C with a quill pen, so SUN couldn't just move it around, because it would break MasterCard or something.
The base FreeBSD system is well thought out, and because it had the ability to, it coalesced into a very coherent system. Man pages are great, everything is where it should be.