It must be polygon which is the cheapest one compared with ethereum and BSC. As far as i know if polygon has more blocksize compared with the ethereum and BSC.
BSC was also very cheap chain but it's still not cheap compared with polygon. I have been sending a transaction on BSC yesterday and it needs at least 20 cents as the transaction fees while i just need to pay a few cents only which was less than 10 cents to create  transaction on the polygon.
You can determine that which chain that will give you less transaction fees from those chain. I personally will try to pick polygon but the problem was if it's not yet supporting a lot of wrapped coin.