Which stable coin is better?

I'm curious about the world of stablecoins, and I'm trying to understand which one might be the best fit for my investment portfolio. Could you please elaborate on the key differences between some of the major stablecoins available today? For instance, how do Tether, USD Coin, and Dai compare in terms of their backing mechanisms, scalability, and overall trustworthiness? Also, I'm interested in understanding how these stablecoins fare in volatile market conditions. Could you provide insights into their performance during past market crashes or periods of high volatility? Lastly, given my focus on long-term stability and growth, which stablecoin would you recommend, and why?