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though it maybe a little outdated, as in the new create a character, there is a trait that adds a flat 15% capture chance to all weapons.
Whip start at 100% incapacitation chance. So for that weapon it makes no difference.
Staff start at 81%. Manhunter brings it up to 96%.
If you don't care which specific enemy you capture, then Manhunter is a good trait because you will incapacitate random enemies with normal weapons, more frequently.
But, if you want to capture a specific enemy, then in some scenarios, it has the opposite effect, where you may end up incapacitating, wrong target.
If that happens, then manhunter in combination with the limitation that you may only capture one enemy of each sex, has suddenly made it impossible instead of easier to capture the intended target.
So, in practice, it forces you to play in a certain way, because you no longer have the option to kill off everyone else first, and then gang whip the target into submission.
Instead you need to incapacitate the intended target first... And because all his friends are still trying to kill you, it needs to be done quickly... And because of that you need to use the staff or other weapons that may accidentally kill the intended target.
For me personally, that makes manhunter a very negative trait.