It comes down to who is doing the coin creation and redemption. In the case of USDC, Coinbase is handling it. In the case of JPMC, JPMorgan would handle it.
The general public's trust in JPMorgan is probably higher than their trust in any crypto company that has yet to exist for an entire decade.
JPMorgan - and other banks - have a huge incentive to run their own "stablecoin" creation/redemption business, because it can in some ways allow them to skirt their reserve requirements, while also possibly netting them a tiny operating profit if they sell newly-minted JPMC above the price they redeem them for (leading to profit on the spread).