I have 4 different computers running RH7.3,RH8,RH9,W2K3 Standard. Unfortunately the fastest one by far, is the one running RH9, so I can't compare very well.
RH9 is running a production level webserver w/ Apache/MySQL/VSFTPd/OpenSSHd.
I would say it is very fast. It probably takes 30 seconds to boot up and be logged in via KDE. And even faster when not running the KDE. Bootup wise I don't see many speed differences btwn RH8/RH9. I wouldn't suggest upgrading, unless needed. Also, I have edited the system init, services, etc to remove alot of the unneeded things. Still a similar server on windows 2K3 takes 1-2minutes to bootup running IIS/MSSQL, so I am happy with my RH.
Intel Celeron 2GHz
Timing buffer-cache reads: 128 MB in 0.44 seconds =290.91 MB/sec
Timing buffered disk reads: 64 MB in 1.99 seconds = 32.16 MB/sec
Its a webserver still setting up for a friend. I which I had something 1/3 as good as this @ home