[bingbing]

There's a wikipedia page with tables of differences: https://en.wikipedia.org/wiki/Comparison_of_BSD_operating_sy...

In my opinion: OpenBSD - Focused on security above all else. Host project of OpenSSH and pf/carp/altq?. Lags behind on architecture support and performance (Previously poor SMP performance?). Primary use: Router/firewall.

FreeBSD - All around features and performance (zfs,dtrace,pf,linux syscall emulation layer). The most popular, and I believe has the most development effort. Popular freebsd derivatives: pfSense (firewall appliance), FreeNAS (zfs storage appliance), PC-BSD (packaged up for an easier desktop experience). Primary use: Desktop/server/firewall/storage/database.

NetBSD: Focused on architecture support. Supports 57 platforms/15 processor architectures: http://www.netbsd.org/ports/. Primary use: support on embedded/uncommon hardware.

DragonFlyBSD: Interesting technologies being developed: HAMMERfs (compare with zfs), application snapshots, virtualized kernel. Matt Dillon's fork of FreeBSD adding the spirit of AmigaOS. Primary use: Compute clusters?

[jballanc]

This is actually a good summary, but it's missing the reason for the DragonFlyBSD fork: light-weight kernel threads. But yes, they've been doing a lot of work around clustering and performance in general.