Use Bep20. These days, TRC20 network is more congested and charges more fee than Bep20. I also think the BSC network is faster than TRON network cos I've been using both and I've been getting faster Bep20 transactions.
this is indeed the case,tron blockchain does indeed cost more than BSC these days even most of exchange have raised the fee imposed towards withdrawal to the tron blockchain therefore personally I think BSC is better, also BSC scalability is so good even though there are significantly more dapps in BSC than in tron the fee remains low, I personally always used BSC these days never tron just because its just better.
Just now i made a transaction of some usdt. Bsc Blockchain was charging lot before but now they made the transaction fee cheap and that's why people using bsc Blockchain more and more. Bsc Blockchain needs some cents to transfer while trx charge a bit higher. But some cents doesn't matter in my opinion. And when its about exchange, then trx network charge 1 to 1.2 usdt in most of exchanges for single transaction while bsc network might be charge 19 to cents something in binance and others exchange will also charge lower like 35cents (some exchange charge equally for bsc and tron network). Both are faster also but now i think bep20 better.
most exchange i found only charges 0.2 USDT for transferring USDT for example and there are layer 2 of BNB called opBNB which has even lower fee if im not mistaken.
things already settled when it comes to finding lowest fee for transferring stablecoin its always BSC, hopefully ETH layer 2 could also follow this footstep of becoming low in gas fee required.