I want a simple way to just set up the plans and have my users redirect to the payment provider's site to put in their card info and get charged.

I would like to get notified when new subscription starts/plan changes/gets cancelled. I want to minimize the amount of code I have to write to do all this since there is already a large list of items I need to address.

I guess so far Amazon and PayPal are the two candidates.

I think Amazon has better rates and API. I would like to get your opinion on the brand image of both companies too. I am afraid when people see the Amazon logo to make a payment they will freak out thinking that the application will be stealing their Amazon information. What do you think?