Any PayPal option should allow buyers a choice between checking out with their PayPal account or with a credit card, but they present that choice in different ways depending on your service.
PayPal Website Payments Standard will give you one checkout button that leads to PayPal, where a buyer can choose their method of payment, credit card or account.
PayPal Website Payments Pro will give you two options in your cart, the yellow PayPal checkout button which will lead to a modified checkout page that only works with a PayPal account (referred to as PayPal Express checkout) and a second credit card checkout button which will still go through your PayPal account but via a checkout page that is located on our servers.
PayPal Payflow Pro works as above, but the credit card button connects to a merchant account at your bank rather than straight to your PayPal account, and that can be used in conjunction with PayPal Website Payments Standard to still allow buyers to check out with a PayPal account.