SS304 is better. There are several reasons below that:

1.The hardness of stainless steel faucet is higher than that of all-copper. The service life of stainless steel faucet is longer than that of all-copper faucet. It does not need to change the faucet frequently, which is more environmentally friendly.

2.Stainless steel faucets do not contain lead, are resistant to acid and alkali, and are not easy to be corroded. They will not release harmful substances to threaten human health after a long time of use. However, the all-copper faucet will grow patina after being used for a long time, which is easy to pollute water quality. The faucet made of copper contains lead element. After a long time of use, a patina will appear, and the color of the faucet will darken, which will affect the appearance.

3.Copper is more expensive than stainless steel. Due to the high cost of raw materials, high-end faucets are generally made of copper. Stainless steel faucets are more suitable for household kitchens. Stainless steel faucets have a price advantage compared to copper faucets.