The selection of administration tools is also similar in the two distributions. However, at first you might think that Fedora has fewer because they are divided between the Application -> System Tools and System -> Administration menus.
Even when the distributions include different applications for the same function, you frequently need to be watching closely to see the difference. The most obvious example of this similarity is Fedora's PackageKit and the Ubuntu Software Center, the tools used for the installation of software packages.
Although developed separately and arranged differently in their windows, the functionality is almost identical, so much so that a casual user is unlikely to guess that Fedora uses .RPM packages and Ubuntu .DEB packages. Although PackageKit has more options for filtering the results that are displayed, the most visible difference is the larger size of the Ubuntu Software Center's icons, which makes the package installer superficially more user-friendly.
For the security conscious, Fedora has an edge because of its use of SELinux, which is more comprehensible and more customizable than Ubuntu's AppArmor. Yet this advantage is subjective, given that SELinux is more complex and harder to use. Someone wishing to learn more about security, or to turn it off, might well prefer Ubuntu's AppArmor.
The default choices in the latest Ubuntu and Fedora releases are both based on a version of the GNOME desktop that represents eight years of constant evolution. Each distribution modifies the desktop, but rarely to an extent that the other cannot duplicate it with twenty minutes of adjusting features and installing software.
Another implication of GNOME's maturity is that apparently little can be done to improve it without radical changes. True, Ubuntu's new default theme may be more commercial than Fedora's in that it reminds people of Windows and OS X color scheme. Yet, overall, I have trouble seeing that Ubuntu's emphasis on usability for the past year has enhanced the GNOME desktop to any significant degree.
Fedora's treatment of GNOME is almost as usable -- and, at any rate, Ubuntu's in-house changes will likely be swept away (together with any advantages) by the release three months from now of GNOME 3.0, which will present an entirely different interface in the GNOME Shell.
No doubt that is why Ubuntu's next release will not include the GNOME Shell.
Of course, users might have other reasons for preferring either Ubuntu 10.04 or Fedora 13. For those who just want their desktop to work, the inclusion of proprietary extras might be a reason for preferring Ubuntu. Others, believing in free software ideals, might prefer Fedora's banning of proprietary elements. Similarly, Ubuntu's faster boot time might appeal to some, while the easy of editing with Legacy GRUB might be the deciding factor in favor of Fedora in some cases.
Only one thing seems sure: your preference of one over the other is going to be based on details that others might dismiss as trivial. Given the common origin in GNOME and the high degree of customization that GNOME encourages, the functional advantage of either distribution is usually going to be minimal at least ninety percent of the time.
To devoted fans, the differences in the distros may loom large, but I suspect that the rest of us are unlikely to agree. These days, a change of desktops within a distribution is probably going to seem a more disruptive change than switching from one GNOME-based distribution to another.