The problem with adding both would be that most people know paypal and so you are likely to have lots of people using that still. Therefore you will still have to pay those fees.

The problem with using just Google is that you might not be able to accept some payments-may lose payments when the person doesn't want to open a Google account. So you will ultimately have a choice to make here.

I have only used Google checkout as a customer, and it was ok. Paypal is faster for me though generally as it logs me in, and I don't have to mess around putting my details in.

If your business is that small, could you possibly have two accounts-one personal and one premier, so that you can use the personal for none credit card transactions (and hence save on that fee).