為什麼荒唐分局種的探員有不同的警徽戴法？ 之前看荒唐分局發現傑克是掛在脖子上的 但是聖地亞哥和警長是別在腰帶上的。 有差別的嗎？

There is no difference legally.

The only difference is:

1. When the badge is at the belt, the badge is usually concealed by the outer clothing, which conceals the officer's identity as a member of the law enforcement.

2. When the badge is on the neck, the badge is not concealed in anyway, which exposes the officer's identity as a member of the law enforcement.