When it comes to questions like this it's important to take the UX hat off and put the consumer hat on.
If you visited a website that let you input your card number and then told you your card type wasn't accepted how would you feel?
If you only had paypal to pay with but went through amazon for a product that sold out quickly, how would that effect your transaction experience upon reaching payment entry?
How would you feel as a foreign consumer with mastercard on a site that only took visa?
It's DIRE to remember you are a consumer as well. It helps put these things into perspective faster.
When it comes to questions like this it's important to take the UX hat off and put the consumer hat on.
If you visited a website that let you input your card number and then told you your card type wasn't accepted how would you feel?
If you only had paypal to pay with but went through amazon for a product that sold out quickly, how would that effect your transaction experience upon reaching payment entry?
How would you feel as a foreign consumer with mastercard on a site that only took visa?
It's DIRE to remember you are a consumer as well. It helps put these things into perspective faster.