I don't really consider either one THAT more powerful than the other. You must not forget that both the Camorra and Ndrangheta consist of various clans that act independently from each other. And while the Sicilian mafia and the Sacra Corona Unita (of Apulia) have a more centralised structure, they as well consist of more or less independent acting groups. Clans within each of the 4 large colloquial "mafia"-type organizations are often prone to feuding with each other over the control of local and international rackets.

The Ndrangheta is the newer "hype" of the moment. They hold a lot of sway in the cocaine trade and they are extremely clannish (and thus not easy to penetrate by law enforcement). As several 'ndrina clans spread throughout Canada and Western Europe (most notably Belgium and Germany) their name became known. Nevertheless I wouldn't say the Ndrangheta dwarfs the traditional Sicilian mafia by any means.

The Sicilian mafia has been weakened due to the heavy prosecution of some of their top names, but I still consider them just as powerful as the Ndrangheta or the Camorra. Sicilian mafia clans are widespread throughout Canada, South America as well as Southern Europe. In the cocaine and hashish trade they may not be as powerful as the Ndrangheta or the Camorra, but more than the Ndrangheta they operate behind legitimate and sophisticated businesses (real estate,...).

The Camorra is a bit less widespread than the Ndrangheta and the Mafia. Outside of Italy they have their main presence in the South of France and Spain. They traditionally had the best connections with the Corsican organized crime clans in France. Like the Sicilian mafia they also operate a lot behind real estate businesses, etc... They are however the most prone to infighting. Camorra clans are constantly at war with each other. This is felt the most in poor Naples suburbs (Scampia, Secondigliano,...) or areas on the outskirts of Naples such as Caserta (for instance the Casalesi- which are said to be the most powerful Camorra clan- finds its origins in the town of Casal Di Principe in Caserta).

SCU clans from Apulia do have an international presence, but in the "Western" areas (North America, Western Europe,...) they are less visible than either the Ndrangheta, Sicilian mafia or Camorra. Of all the Italian criminal organizations they however do have the best connections with the strongest of the three Balkan-based types of organized crime: Albanian OC, Serb/Montenegrin OC and Bulgarian OC. They work a lot in weapons trafficking, as well as human trafficking and some drug trafficking that passes through the Balkans (heroin through Northern Albania & Kosovo and Serbia & Montenegro; cocaine and synthetic drugs through Bulgaria). The Montenegrin port city of Niksic has a known presence from the SCU as well as from Kosovo and Belgrade-based groups.

The SCU is internationally the weakest (although they're still quite strong in their own right and are still among the top criminal organizations), but the difference in power between the Ndrangheta, Sicilian mafia and Camorra is a lot smaller. These 4 are however without question the main Italian types of OC. In Sicily there was once the Stidda, but they've been more or less absorbed by the Mafia. The Mala Del Brenta in the Veneto region is pretty much done.