i've used all 3, and if installed correctly by a linux guru (i.e. not only do you need to know what you are doing but you should take the time to do it right and lock it down security wise), they all work fine. If this truly is a "production server" you won't care about graphical anything and all that will matter is ssh, an email program (i like qmail myself), aolserver and postgresql... all four of these programs run fine on any of them, since the only drivers you should care about are network card drivers and possibly scsi drivers any of the new USB/etc. support will be pretty irrlevant... The advantage of RH9 is if you buy into this auto update stuff from RH it will be supported longer than the other two since RH has given its "personal desktop" line of software a very short support life. If you are compliling your own packages of the 4 important services available to the public then you really don't need to worry about many other updates (i.e. who cares if a new version of emacs is available if what you are using works fine)... and binary distribution won't matter. Once OpenSSH comes out with a necessary secuirty fix you'll just have to recompile.
oh yeah, and as a secondary thing, if you run an email server your speed will increase significantly if you install a DNS cache only accessible to local host (i.e. you won't open it up to security issues).
