Which is the best domestic/continental level?

Prospects often usually move up during their careers by going through the rungs to world title level, by fighting domestic and continental fights. However, a thought came to me - which of these domestic/continental scenes are the best/most competitive? For instance, is European level better than North American? Asian/Pacific level and African level are less spoken about and generally produce less quality, so I suppose the argument is between European and North American level, it would be interesting if there was some evidence to suggest fighters at the top of those levels are more successful at world title level eventually. Also, perhaps we could make a comparison regarding British domestic level and the scene in the USA. Discuss :boxing: