Advantage in Europe is that all JAR23(FAR23) JAR25(FAR25) aircraft require a type rating for both crew members. Plus some single pilot aircraft defined by authorities.
It simply makes life easier as you know what training the other guy got before sitting in his seat. Additionally a type rating requires a skill test defining a certain level of training. To get a type rating for multi-pilot aircraft the minimum requirement is CPL/IR with multi engine rating (MEP) and completed initial CRM and MCC (Multi Crew Cooperation) course including SIM sessions.
Sounds familiar to the FAR's? Just a much clearer version to say: Hey guys - want to fly a multipilot aircraft - take a TR - period.
Maybe the solution as some pointed out cautiously is as most of the time somewhere in the middle. Both systems work - both have their flaws - both have advantages.