Which cell balancing method (active or passive) is best for low-voltage BMS (Battery Management System)?
A general remark: There is no such thing as a perfect system. Every technical system comes with a set of complex tradeoffs and one needs to decide which parameter to favour.

There is not just one method of active balancing. Every active balancing system will come with its own set of complexities and benefits. I personally only looked into the tradeoff between charging efficiency and system complexity.

When I last looked into this tradeoff (3 years ago) i kind of discovered that active balancing was a bit overhyped. In most cases you will not really see a large enough difference in charging efficiency to merit the increase in system complexity.

Every published work that tried to show (or sell?) active balancing is a good idea first placed the cells into an extremely unbalanced state (>10% state of charge difference). And even with this massively unbalanced stack they really did not show huge improvements to the charging efficiency compared to the much simpler passive balancing option.

My own personal experiments showed that batteries really do not get out of balance to that degree unless you have a general system problem. In which case balancing is not the way to go but you really need to fix the problem itself. (If you try to fix it with balancing then you will still have to deal with the problem of different ageing speeds that may result from such a systematic problem)