The transaction fees of BEP-20 and TRC-20 are almost similar, there is not much difference but what I have noticed that transactions on TRC-20 are processed quicker. I am attaching below a link of site that  shows the real-time gas fees for USDT transfer to various networks, such as Etherem, BSC (BEP-20), polygon and Tron (TRC-20).

https://gasfeesnow.com/?ref=pixeljets.com