Tether coin (USDT) is the most popular and controversial stablecoin, a cryptocurrency tied to a stable asset such as gold or units of a fiat currency.
Supply 4,108,044,456 USDT
Volume 17,077,127,568 USDT

USD Coin (USDC) is a relatively fresh stablecoin pegged to the US dollar. It was launched on September 26, 2018, in collaboration between Circle and Coinbase.
Supply 426,686,876 USDC
Volume 160,993,544 USDC

TrueUSD (TUSD) is a fully collateralized, legally protected and transparently verified ERC-20 token.
Supply 190,126,990 TUSD
Volume 118,105,273 TUSD


As you can see the most used stable coin is Tether (USDT)

And be careful using TUSD, is an ERC-20 token and not all exchanges admit that coin.

Check in your exchanges where you use to trade what is the coin they use, withdrawal fees, and make your choice, sometimes you can enjoy a little arbitrage.

Info taken from

https://cryptonews.com/coins/tether/

https://cryptonews.com/coins/usd-coin/

https://cryptonews.com/coins/trueusd/