It isn’t easy to give a generalized answer to this. Different payment gateways serve different purposes. For example, PayPal is one of the most used payment gateways for eCommerce sites due to its flexibility. On the other hand, Stripe is a US-based payment gateway service which is used in 39 countries all over the world. So, in case you need broader coverage, PayPal is best for you.
Apart from that, Worldpay is another payment gateway available only for business. However, Worldpay is cheaper than a merchant bank account. So, here Worldpay is best if you need a gateway for business at a low cost.