Foe web hosting you really won't see the difference.between Linux+Apache and FreeBSD+Apache. Everything will seem the same to you. When you get inside the shell via ssh or telnet they will be a little different, but if you are just FTPing you'll never know the difference. FreeBSD is suppose to be a superbly stable OS and a fantastic memory manager. I'd run away from the NT box.
As a "casual user", you'll find that almost any two unix based systems by different manufacturers are much more compatible to each other than any two Windows systems by one single manufacturer... ;)
In fact, this impression will get even stronger when you start programming for those boxes. The main differences will surface on a system administration level, where many configuration files either have a different format, or are located in different places.