This is probably a FAQ somewhere, but anyway...
Linux, *BSD, and Solaris are totally different OSs though they share similar tools and applications. There's a long history behind each of them that I won't get into.
As mentioned, for the casual user (i.e. not running a high-load server), either Linux or FreeBSD are similar enough that it really just comes down to the installation, applications, and hardware support.
Linux is more popular and therefore has a lot more contributors (and thus more hardware and software support). Many programs like WINE are developed on Linux first then ported to other OSs like *BSD, so you get to stay on the bleeding edge (unlike the OpenBSD port of WINE, which is 3 years old...). Nevertheless, FreeBSD is also popular and keeps up fairly well with the versions, so it's a tough choice.
I currently am playing with Slackware Linux on my laptop. I wanted to try FreeBSD but it doesn't support CardBus yet 🙁