When are passive preamps better?

If your audio source has a robust output stage capable of delivering the required energy (voltage & current), then a passive preamp will most likely yield excellent results that will rival most active preamps regardless of price point,

When are active preamps better?

If your source has a weak output stage, an active preamp will likely mitigate this weakness to some extent resulting in better sonics than a passive preamp.

How do you know which is better?

Try a passive preamp.
Try an active preamp.
Then you’ll know.
Because there’s no other practical way to know how well your source performs