贝宝快递与网站支付标准之间的API差异。

I'm trying to understand the API differences between Paypal's Express Checkout and Website Payment Standard. I know the user-facing differences (Express Checkout forces you to have a Paypal account, while Website Payment Standard also processes credit cards), but I don't know the differences between how you can interface with them programmatically, specifically from a Rails app. Active Merchant says that it supports Express Checkout but doesn't mention Website Payment Standard. For recurring payments, I found I'm trying to understand the API differences be