Note that some payment processors can only be used with our Buy Now buttons and may have other limitations in which of our features they can support, whereas others allow full support for our shopping cart and other features:
http://www.e-junkie.com/ej/help.payment.processors.htm
Each payment processor we support in an independent third-party service, so any information we might provide about their own terms and conditions, features, fees, etc. would be secondhand and therefore quite likely to become inaccurate or out-of-date. You would do best to get any information about them directly from the original source.
PayPal Pro and Authorize.Net support direct card-based checkout where the buyer enters their card account info at checkout to pay you directly. Google Checkout works very similar to this from a buyer's perspective, only adding a login and password field to create a new account instantly if the buyer doesn't have one already. PayPal (non-Pro) usually offers a direct card-payment option without requiring a PayPal account, but they don't always offer that option, and there is no way to force that option being offered every time.