"This is good milk."
Translation:هٰذا حَليب طَيِّب.
From my limited understanding both exist in Modern Standard Arabic and at least some colloquial dialects. جيِّد is more likely to refer to something that is of a high quality, whereas طَيِّب is more likely to refer to something that is enjoyable (and delicious when relating to food).
It's a useful distinction because the word 'good' in English has such a broad meaning.