Which eCommerce payment gateway will you integrate to your online store and why?

I think it will be one of such gateways as PayPal Pro, Braintree, Authorize.Net or 2Checkout.
There is a huge amount of different, but I have read about the most used of them here. And, as a result, I stopped my choice on the above-mentioned.
What do you think about all of them and which one do you prefer? And why?
Thank you in advance!