Ubuntu is known as Linux for Human Beings, because it's driven by the philosophy that "software should be available free of charge, software tools should be usable by people in their local language and despite any disabilities, and people should have the freedom to customize and alter their software in whatever way they see fit"
PC-BSD, on the other hand, "has been designed with the casual computer user in mind. Installing the system is simply a matter of a few clicks and a few minutes for the installation process to finish. Hardware such as video, sound, network, and other devices will be auto-detected and available at the first system startup. Home users will immediately feel comfortable with PC-BSD's desktop interface, with KDE 3.5 running under the hood. Software installation has also been designed to be as painless as possible, simply double-click and software will be installed"
Having used both operating systems extensively, PC-BSD is the one I recommend and the one I install in desktop environments. If you've used Ubuntu before, but haven't tried PC-BSD, give it a try. The increase in responsiveness (i.e., everything seems to just run faster) and ease-of-use will surprise you.
In this article, I'll compare Ubuntu 7.04 (Fiesty Fawn) with the (as of this writing) upcoming release of PC-BSD 1.4.
http://www.linuxdevcenter.com/pub/a/linux/2007/08/23/linux-vs-bsd-whats-the-difference.html?CMP=OTC-0O724Z062301&ATT=Linux+vs+BSD+What+s+the+Difference