Easily think, 안녕히가세요 -> honorific / 잘가요 -> talk down
Both means "say good bye!"
Thanks so much. 고맙습니다.
for more information, 안녕히 가세요 is used for elders or if you're in a formal situation. And in my opinion, 잘 가 is more used than 잘 가요. When Friends say goodbye to each other, they usually say the word '잘 가'!!