Which ranking is more meaningful for post-doc students?
None of them. At the postdoc level, you should already be familiar with the people and research groups in your field, at least at a basic level. Go where there is someone you want to work with, and maybe a good active research group, irrespective of the ranking of their university. That ranking could have been achieved because the university is great in a completely different research area, or because it has good conditions for students (as a postdoc, you don't care about this). And, as you state yourself, at high detail level many rankings are bullsinaccurate anyway.