Duck liver is good.

Duck liver contains more vitamin A, vitamin B2 and vitamin B12 than chicken liver. These vitamins are essential for promoting a healthy immune system, maintaining vision and nervous system function. Moreover, duck liver is also rich in iron, zinc and protein, which helps to supplement the nutrients needed by the body. In contrast, chicken liver, while also rich in nutrients, is relatively low in vitamins and minerals. So, all things considered, duck liver is better.