The verdict
For a small business that needs to be paid quickly, pick PayPal. A payment link or an invoice needs no website and no setup, and customers who already trust PayPal may be more willing to pay. It is a sensible extra payment method next to cards for most consumer-facing shops.
If you run recurring revenue with usage charges, credits, upgrades mid-term or quotes, pick Chargebee. That is billing logic, and PayPal is not built for it.
If you want tax carried for you, neither does that as a merchant of record would. Look at Paddle for that. If you want to use PayPal with Chargebee, check that your gateway setup is supported before you plan on it.