The correct similarity between prokaryotic and eukaryotic cells is:
Both prokaryotic and eukaryotic cells are filled with cytoplasm.
Prokaryotic cells do not have a nucleus or membrane-bound organelles, while eukaryotic cells do. Prokaryotic cells typically have a cell membrane and often a cell wall, but not all eukaryotic cells have a cell wall. Therefore, the statement about cytoplasm is the accurate comparison.