Ask HN: How to choose between Stripe and Amazon Payments?

Debating between these two for subscription payments for a site I'm working on. They both cost the same, no setup fees, obviously both are very established companies so I'm having trouble picking between the two.

- Why did you pick one over the other?

- How has your developer experience been with each if you've used both?

- What else should I be asking myself before I decide?

I suspect that using an Amazon login and Amazon Payments would lead to a higher conversion rate, but I don't know by how much and can't prove that. Perhaps the chance of higher conversion alone is worth some extra dev time to do the setup (I'm assuming AMZN is slightly less easy to setup because of the general increased complexity of AWS services over others like Digital Ocean) but I could be totally wrong.

And this leads to another question: why don't I see more sites using Amazon logins? I almost always see Google, Twitter and FB only.