IMHO a beginner has very few choicie. He should choose ubuntu. Fedora is about as good as ubuntu for beginners, but it is more difficult to find other users to get help. A beginner may choose fedora if he is using redhat at work and could get some directions from IT staff. The variants of ubuntu introduce some confusion and do not give much benefit in return. The other distributions do not fit beginners (either lack of polish or lack of users or both).