Jai_Ganesha said: ...both are 4" tall...
I just finished buying a case of pots...
We need more information than just the height of each pot. Along with the height of 4" you have to know the diameter at the top of the round pot and the measurement at the top of the square pot.
You can download the catalog for East Jordan Plastics. In the catalog you will find the height, diameter, volume/capacity, etc.
Hope this helps.