USDT settles on TRC-20, TRX settles on TRON — confirmation times for each depend on current network conditions, so neither one is reliably faster at every moment.
Both USDT and TRX require a funded wallet where a card doesn't, but either one still lands Stars in about the same time as a card payment would, without the billing form.
Whether the fee ends up higher on TRC-20 or TRON changes with network load — check the fee shown before confirming either payment.
It depends on current network fees on TRC-20 and TRON, not a fixed difference — check the fee shown at checkout for either.
No, TRC-20 and TRON each charge their own transaction fee on top of the order, separate from the Stars price.