the reaason why i ask is because TRC20 is cheaper to use and more popular then USDT ERC20
I don't know if it's more popular, but it's certainly up their among the most used networks for the tether stablecoin. What you said about it being cheaper is not true, though. To send USDT over the Tron network, you need 13 TRX if the receiving address already has some TRX on it or 27 TRX if it doesn't have any. That's around $3.5 to $7 per transaction. This amount doesn't change. Ethereum's fees go up and down. If they are on the cheaper end, you can send ERC20 tokens for ≈ $0.50 in ETH. If they go up, you are looking at $1 to $3 per transaction in normal network conditions.
My personal view was that stablecoins are the weakest link in the cryptocurrency world, because not only are they completely centralized and in some cases probably "printed" out of thin air - they are also a direct threat to fiat currencies and as such represent direct competition to central banks.
Unfortunately, they are a necessary evil we have to cope with.