Express Checkout is the closest to standard.
The way express checkout works is:
-User Files in checkout form at checkout.php to set the shipping address
-they then go to the paypal site to set up the transaction payment details
-they are passed to the pp_confirm page where the transaction is processed, if the transaction failed, they go to the pp_checkout_failure page.
if you set up the wizard to save the order to the DB and send an email, those behaviors are triggered if the transaction is successful, then the user is directed to the pp_checkout_success page.
PayPal Payments pro is 2 checkout services:
- Direct Checkout. In this method, the user enters the payment details while on your site
- Express Checkout
So with either choice, you still get paypal express checkout, it's just that with Payments Pro, you also get the Direct Checkout option.