I don't trust this two but if I should pick one of them, It would be definitely Tether. Tether is first of its kind. And it was usefull for bear market.
After USDT one by one many coins has came. TUSD, PAX, Gemini USDC... Why we need that? Tether was enough.
No, we need more stablecoin in this market to make the market more competitive and make it more stable. Just like we were too dependent on USDT and its price was easily
Same thoughts about Tether, but I disagree with you about the rest part about stablecoins. To me we need as many stablecoins as possible for diversification. We can't be sure at any of them, so it would be reasonable to have them all to reduce risks.