USDC is more reliable than USDT, actually USDC is getting more support within the European market while USDT is getting excluded because of their opacity.
USDT is only afloat as one of the top tokens in the market because it continues to be widely affected among people in third world countries.
If I had to keep an important amount of money in stablecoins, then I would go for USDC or some decentralized currency, reminiscent to what DAI used to be back when it was launched.
Anyways, many people argue Tether is supposed to be avoided at all cost, and I would agree with if the holding was in the long term.
USDT has always been shady from the start (lack of transparency, sudden issuance of new units (printing), etc.). I can't believe it's still the #1 stablecoin on the market. USDC, on the other hand, is more "regulatory-compliant" and trusted by the community. USDT is more like a trading tool, than some serious, long-term investment. For guaranteed security (sort of), choose USDC instead.
Either way, nothing beats cold, hard cash. Stablecoins are new and widely unproven. Even if USDC is the most regulatory-compliant stablecoin on the market, that doesn't mean it won't fail in the long run. After all, there are no investor protections or guarantees of any kind. When you keep your money in the bank, it's insured by the government. At least, in the US. So you'll be able to recover your money if something bad happens in the long run. Hopefully, regulators scrutinize stablecoins more throughly to avert a crisis further down the road. Just my two stats.