If you want to try out both PayPal and cards, you should probably use Braintree Payments. They even process your first $50k for free, which is great for startups. Uber and Airbnb use them, see how seamless those checkouts are?
Are chargebacks a common occurrence?
Are they common? Depending on your business, they might not be that common to you. But ALWAYS expect some chargebacks.