Oxford 100%. If you're more of an elitist, prefer an atmosphere with strong-held traditions, then Oxford is a much more preferrable choice. However, I enjoy a community with greater diverstiy in terms of a vartiety of subjects and size. Oxford is larger, and provides much more subjects; the Oxford Union and debating chamber provides greater influence than Cambridge, inviting and hosting a plethora of intellectuals which have made enormous contributions.
However, there are some "celebrities", which have only recieved admission into Oxford because of their identity, or being a nobel prize laureate, not because of skill.