You can find out the most reliable stable coin according to their market cap. So which stable coin has a big market cap that means that is the most reliable coin IMO. Here is some stable coin and their market cap according to
https://coinmarketcap.com on 29.10.19
1. Tether USDT $4,116,948,481
2. USD Coin USD Coin (USDC) $472,958,897 USD
3. Paxos Standard (PAX) $260,218,312 USD
4. TrueUSD (TUSD) $180,749,382 USD
5. Dai (DAI) $89,252,171 USD
6. USDK (USDK) $27,900,098 USD
7. Binance USD (BUSD) $21,340,817 USD
8. Gemini Dollar (GUSD $7,915,479 USD
9. USDQ (USDQ) $5,471,711 USD
10. StableUSD (USDS) $3,601,028 USD
These are the top 10 Stable coins according to their market cap. So There is no hesitation to say that USDT is the best reliable stable coin. It's my personal opinion. So tt is my personal opinion, and may not be anyone else's