From my personal experience, Fedora Core 4 itself is not much slower than other systems. What matters is how it is configured.
Currently i use ubuntu 5.04 (upgrading right now, actually, to 5.10) and I notice some speed improvements upon Fedora Core 3 (the last one I used), but that is most likely because I know more about linux systems, and do not currently have server software and everything else running that I didn't need in Fedora Core 3.
The only reason I'm choosing Ubuntu over fedora core is trivial; They are both great Linux/GNU Operating Systems.
When I first converted to linux 3 years ago, I liked Redhat's GUI config programs. There are not quite as many in Ubuntu, and they are not quite as nice as now-Fedora's, but I don't need them anymore, really.
SuSE is a very nice, well polished distro that I hope to test out soon after setting up ubuntu 5.10.
In the past, every major distro release I re-asses my choice of distro. Back with redhat I compared it to mandrake, and redhat won. I compared fedora with slackware and suse, fedora won. FC4 came around and when I compared it with ubuntu 5.04, ubuntu won in my mind.
Are there any tremendous differences? not really. They are all linux. They all run fast (on my AMD 2600, 768mb DDR266), they are all stable, and they are all easy to install. The only differeces are their user-friendliness. That part I won't comment on, because I can no longer responsibly make claims to user friendliness as a Linux novice would notice it.
