Short answer: Kronos for banking + crypto; Coinbase for pure exchange.
Coinbase is a custodial exchange charging ~1.49% retail. Kronos is a non-custodial wallet inside a US neobank, with $0 platform fees on Kronos Pro and a banking layer (debit card, savings, ACH, pay advances) Coinbase does not offer.
Use Coinbase if you need a high-volume custodial trading account with deep order books. Use Kronos if you want crypto inside the same balance you spend with a debit card.