I'd go FreeBSD, if you are comfortable with it and/or your control panel works with it. Redhat 9 sucks badly. Ask myself of Josh
Plus that is being phased out, so your only real option is enterprise (might as well buy a win2k3 server) or Fedora. So far I'm extremely pleased with Fedora, but time will tell.
I've only avoided FreeBSD in the past because for a while they had some real troubles getting cPanel to work properly on it, but I think FBSD has much better support for most major control panels now, but I haven't been following too closely.