Also, Lumens, being the total energy, is constant for a given light and setting, whereas Lux varies with distance from the source, of course, dimmer father away.
Then the question is what Lux value and at what distance from the light is it specified?

So, by themselves, neither Lumens nor Lux is a good way of comparing lights for how good it will be for riding. The beam pattern, if well focused might look good as having a high Lux value, but be too much of a spotlight when on the bike.
The best way to compare is to try it, and/or search for reviewers beam pattern photos.