On Binance exchange, BEP20 transactions are cheaper, but it can be of the same fee on other exchanges. In over all that I have seen, BEP20 is cheaper.

On noncustodial wallet, BEP20 is cheaper.

Most widely used for USDT, TRC20.

BEP20 should be cheaper, but TRC20 is more widely used. I’d go with the latter if the plan is to hold this for the long term, there’s is no point in holding something that’s only supported by one centralized exchange, and a couple of DEXes.

Bep20 is cheaper now because trc20 now charging more fee and it is remain no cheaper network. 2-3 years later TRC20 was most cheapest network and sending fee was just one trx(0.02$) but I checked one year ago by sending usdt to other addresses and trc network charged 2$ per transaction which is higher than many network.

BSC network fee is just 0.05$-0.1$ which is very low as compared to TRC. If you use Matic then it is cheaper than both.