If this is your very first experience with linux, and you are limited only to these two distributions, I certainly would recommend Ubuntu over Fedora.
They each have their pro's and con's, but Ubuntu/Kubuntu most likely will require less "expertise" to get up and running, and Fedora is aimed mainly at geeks and those that like to tinker with their machines more than average.
The great thing about linux is that, if you don't like the distribution you're using, you can always change to another, free of charge
Just my thoughts; your mileage may vary.
Hope this helps.
