What, specifically, do you see as more stable about BSD over Linux?
Nothing really... Just NetBSD is infamous for being uber stable. Linux under severe load can behave, well strangely. I have seen BSD boxes with loads up to 12 (Single Core as well so that's 12x optimum load) and still behave sanely.
Not saying you're wrong, but just personally I really haven't run into much in the way of stability issues with Linux servers, and it always seemed to me that BSD would have been giving me more headaches - most notably in the area of hardware support.
I think it depends what your doing with the servers. Over the last lot of years Linux has got 100x better, but back in the good ol' days BSD was where it was at. Further to that, hardware was a bitch on both to support. It was a case of choose your weapon.
I moved to Arch Linux because of its BSD like nature.... I guess I just like the way BSD does things.... And Arch rocks.
BTW: I have started recently using Arch on Servers as my faith grows in the distribution.