For several years, users' experience in Linux has depended more on the desktop than the distribution. Fedora 14 and Ubuntu 10.10 (Maverick), conveniently released within a few weeks of each other, do little to challenge that assertion. Changes are occurring in the back ends, but, from a users' perspective, both these recent releases are hard to review because the interfaces have barely changed.
However, comparing these recent releases does show some distinct differences in emphasis that might affect your decision about which one to use. The difference is not just that Ubuntu is more commercial, but that it also modifies what it ships far more than Fedora, and, increasingly, tends to be developed with the assumptions that users will be content to work in the ways that the software dictates.
As contemporaries, Fedora 14 and Ubuntu 10.10 provide an apt comparison. In past releases, the two distributions have been the most downloaded distributions on Distrowatch -- although Ubuntu usually has 20-40% more downloads -- and there is no reason to think these latest releases will be much different.
Although other distributions such as Mint, openSUSE, and Debian are downloaded almost as often as Fedora on Distrowatch, Ubuntu and Fedora remain consistently the most popular distributions.
Probably, too, they are the largest distribution projects in terms of participants as well, despite the obvious differences in branding, default desktops and software selection.
Both Fedora and Ubuntu show strong efforts at branding. Fedora uses its logo to indicate progress at bootup, and has a tradition of producing new artwork for each release. Usually, the artwork is airbrushed and dramatic, and does not stray far from Fedora's standard blue theme.
Fedora also has a tradition for naming each release: each new code name must have some sort of free association with the previous one. Yet this tradition has never caught the popular imagination of the free software community. For instance, how many people know that Laughlin is Fedora 14's code name, let alone its relation to Goddard, Fedora 13's code name?
By contrast, Ubuntu's habit of alliterative code names consisting of an adjective followed by an animal in alphabetical sequence is so well-known that it is eagerly anticipated, and the subject of endless jokes.
In fact, as might be expected from a commercial company, Ubuntu brands far more extensively than Fedora or any other community distribution. Ubuntu's current Light theme is not only the result of extensive effort, but heavily color-coded to reflect subject both on and off the desktop, although most of its subtleties probably escape the average user (as they do me).
Both Fedora and Ubuntu have long since taken to omitting references to Linux on their home pages. However, in the last release or two, Ubuntu has gone even further and taken to emphasizing its name on the desktop.
For instance, the main package manager is now Ubuntu Software Center, as opposed to Fedora's Add/Remove Software. Similarly, Ubuntu's cloud services are called Ubuntu One -- a name which not only has Orwellian overtones of Airstrip One, but also makes its purpose obscure in the menus, making it an exception to Ubuntu's general emphasis on usability.
Ubuntu's branding is still mild compared to that of Windows. All the same, it can be jarring to long-time users of Linux, where such commercialism is still relatively uncommon. Yet perhaps such branding is the necessary price for profit -- and, of course, most of Ubuntu's branding's, like most of Fedora's, can be removed if you prefer.
The latest Fedora and Ubuntu releases are both based on GNOME 2.32. Neither has changed much from the last half dozen releases.
Broadly speaking, they look much the same, both sporting a top and bottom panel and the familiar Applications-Places-System trio of menus in the top left. Many of the differences are minor, such as two virtual workspaces in Fedora compared to Ubuntu's four, and the placement of the package tool at the bottom of the Applications menu in Ubuntu, but at the top of the System -> Administration menu in Fedora. The largest difference in the placement of these standard elements is that Fedora's Application menu includes a System Tools sub-menu, whose contents Ubuntu shifts over to the System -> Administration.