Thanks Aitch, that was just the kind of graphical comparison I was looking for. Helps to make things clearer.
Yes, I originally looked as JFS as well, but at the time it was still in flux.
I originally used a guide written by Jarod Willson which was my first major foray into Linux and at the time he suggested XFS. The wiki entry based on his guide now says ext4 looks good as well since it is stock in Fedora, but I have tried to stick by "if is is not broke, don't fix it".
Of course, like most of us here, I can't leave well enough alone and usually "fix it till it is broke" then back off one quarter turn!
(Mr Willson has since started working for Red Hat and is now maintainer of LIRC and over saw it's inclusion in the kernel, so I guess I was lucky to take advice from a good source from the start)
(by the way, it's a lower case "L" not "I")