Similarities: They both have a generally dome-shaped shell. They both require ladders for humans to reach the hatches near the point. They were both "built" for the same purpose, fictional or not, and both achieved the same goal.
Differences: One is functional, the other is not. The Apollo craft is smaller and more compact, with more advanced structure and appendages. The columbiad is much larger and has a smooth outer shell. The columbiad could hold many more people than the Apollo did.