[dp7531]

One big difference between PayPal and Google Checkout has to do with your users signing up for an account on their system. For Google Checkout, your users will also need to have a Google Checkout id before they can complete a payment. On PayPal Website Payments Standard (and I believe Pro as well) they can pay by credit card without being forced to create a PayPal account or log in to PayPal itself.

[dav-id]

This is important because if you are targeting B2B sales then most wont be able to / wont want to create a google account.