What’s the “best” international scale?

There's no single answer

It’s important to consider cultural differences in response to research scales when designing surveys and interpreting results.  This often entails some compromise on the number of points on a scale as 5 point scales typically won’t give enough variation in high scoring cultures and 10 point scales can leave too large a cultural gap between nations. Depending upon the market mix 7 point can work well.

Chinese / Japanese research participants have been shown to have a greater preference for mid points and to be less likely to use scale extremes.  

North American participants are more likely to agree or give a positive response to a question and to display extreme responses often resulting in higher average scores for North American responses versus Northern European ones for example.

Many studies have highlighted that the Millennial generation displays different attitudes and behaviours to previous generations.  They typically exhibit lower trust in people and organisations and higher importance on the societal contribution of employers and companies that they choose to buy from.