Stablecoin may all look the same, but this is not the case. A distinction must be made between CEFI and DEFI ones.
The DEFI ones are censorship-proof, decentralized, unregulated and not collateralised by real assets. In these cases, smart contracts are used.
Let's see the best known, seeing their positive and negative aspects.
Tether (USDT): this is the most used stablecoin in absolute and third as market capitalization on a global level. This stablecoin is theoretically coined in a 1: 1 ratio with the dollar.
For example there are USDT 8 billion -> somewhere there will be $ 8 billion in a bank account.
In reality it is not quite so because Tether uses fractional reserve and only 74% of USDT is covered by fiat currencies (the remainder is used as loans and other issues, this poses the risk that liquidity is not always available, bearing the insolvency risk).
It is an unregulated coin, however accepted on Binance and on many other exchanges.
USD Coin (USDC): linked to the value of the dollar and collateralised by underlying funds in a bank account (even here it is possible to make fractional reserve). It complies with American laws and there also appears to be an independent law firm that controls the assets that collateralize USDC (a report comes out once a month). It is open source. Much used on CEFI platforms (BlockFi, Nexo, Celsius Network).
Paxos Standard (PAX): this stablecoin is always linked to the value of real assets (dollar in this case). The company also issues Pax Gold (crypto that collateralizes real gold). In this case we do not find fractional reserve therefore the real assets are entirely present in the current accounts. Little present in exchanges.
Binance USD (BUSD): always provided by the company Paxos and in collaboration with Binance. Similar to PAX and linked to the Binance exchange.
TrueUSDT (TUSD): they seek to guarantee maximum transparency and trust to users. The funds are 100% liquid and not kept by the company that provides TUSD but by escrow (third party companies).
Nobody can access the funds unless they have the authorization of the TUSD owner.
Gemini Dollar (GUSD): always a company regulated by US laws.
Centralized, transparent and there is always a monthly report showing the presence of liquid funds.
Dai (DAI): the main stablecoin linked to DEFI. It is not tied to physical assets but completely virtual. Through a lever of interest that aims to balance supply / demand on the value of 1 dollar, it remains constant. It is created on Maker by collateralizing Ethereum and others ERC20 (BAT) using Chainlink (LINK) as an oracle.
The virtual assets are blocked, I ask for the loan, receiving DAI (2/3 of the blocked collateral; the risk is the high volatility of the blocked assets and therefore the liquidation risk). It is not censurable and there are no regulations to protect users. It is the most volatile stablecoin.
sUSD (SUSD): this is the stable of the Synthetix platform (which concerns synthetic assets). It is possible to trade on collateralisation of crypto with traditional assets (gold, dollars, BTC, tesla, etc).
mStable USD (MUSD): this is a stablecoin collateralised by other stablecoins.
Reserve (RSV): tries to develop from the value of the dollar through an inflation proof mechanism (with constant purchasing power). Aim for complete decentralization.