Which is the Better Tonearm - Pro-Ject or Rega?

Which is the better arm in your opinion, the Rega 251/202 arm that's also found on the Rega clones (Edwards Audio TT1 for example), or the Pro-Ject arm found on the Debut/Essential and Pro-Ject clones (such as the Music Hall MMF 2.2).

Does Pro-Ject's carbon arm (as found on the Debut Carbon) change your position on the comparison?

Thanks!