The measurement of lights is quoted in different units, and can be measured at different distances. Also a diffuse wide beam is a diffent animal altogether from a tight beam, ar a filtered beam such as those available in Germany
Even light with comparative values can be different on the road
The best way is to google some of the sites that do comparative images such as
road CC
This allows you to put an "identical image" of two lights next to each other and compare their effectiveness
Torchythe battery Boy does something similar, but you do not get the side by side comparison