Most everything between the two are essentially identical.
I grew up in a neighborhood (Detroit) that was about 30% Ukrainian, 50% Polish background, here, parents were first generation American-born. Go³ómki are a classic difference that I noticed between the two. Ukrainian's fill them about 8/10ths rice, Poles about 8/10ths meat (ideally 1/3 ground beef, 1/3 ground veal, and 1/3 ground pork). The Ukrainian ones are way bigger than the Polish ones. Otherwise they taste the same. Pierogi are exactly alike, far as I could tell. I never saw a Ukrainian (or myself) eat czarnina. Poles made the best babkas, Ukrainians I knew there, put together tortes to die for. I spent many a cloudy depressing early March day making pisanki at my Ukrainian neighbor's house. Poles just used Paa's easter egg dye on Good Friday.