PayPal is one of the oldest and definitely the most popular payment gateway and is used all around the world. This is the first gateway most people mention when asked about payment solutions. Although it is still the most popular, the competition is growing.
Braintree was recently acquired by PayPal, but still offers the service under its own name. These two are basically different solutions, and are chosen for different business cases.
Stripe is one of PayPalís closest competitors. The developer-first approach ensures that Stripe integration is flexible and robust, and can be adjusted for different business cases.
Adyen is a payment gateway headquartered in the Netherlands. It is very popular among online businesses all over Europe, but some international giants also use the services of Adyen.
Pin Payments is a local solution that supports online businesses in Australia and New Zealand only. It offers a high-quality service at a reasonable price, which makes it a perfect solution for companies that operate in the region.