It's safer cus there are hundreds of crypto exchanges that exist, in jurisdictions all over with varying levels of regulation or compliance. Many of which have run off with customer funds. You can always be sure that your funds are safer in your own wallet than on an exchange.

However, USDC is issued by a consortium spear headed by Coinbase which is a publicly traded US company that has a wealth of regulatory compliance hoops they jump through, and have routine independent auditors track the reserves of USDC.

But youre right in that there's elements of trust that you need to place.

Multiple parties need to fail for USDC to not be tradeable or redeemable to USD - holding in an exchange just requires one party to fail (exchange hacked, exit scam etc.)

It's pretty simple risk logic.