Of the three distributions, I think Fedora is closest to the cutting edge, with openSUSE and Ubuntu both fairly close behind. However, Fedora and Ubuntu have relatively short support cycles with Fedora releases usually supported for about 14 months, Ubuntu 15.10 for just nine months and openSUSE 42.1 will receive three years of support.
The best distribution for the job will depend on the person and, of course, the role the distribution is to play. I think Fedora is aimed mostly at more technical users and people who like to tinker. Ubuntu is aimed squarely at Linux newcomers who generally want to just use their computer and openSUSE appears to be aiming at a sort of middle ground: people who have a little Linux experience and want options, but also want reliability and longer support cycles.
