To those that offer the customer the ability to pay on your site by credit card and paypal, what would you guess is the percentage breakdown in the client's choice? even btw CC and paypal? most choosing paypal?

For me my sales seem to average out, both PayPal & 2CO are used about the same.
Really I would recommend that you always use another method for Credit Cards such as 2CO and not just stick with PayPal as it will limit your client base.

2Checkout are about 90% of our sales, 8% are Paypal and 2% are Checks/Wires.

paypal is recommended, because its more safer for customers.

For us it is about 60% CC , 40 % Paypal.
I wouldn't recommend 2CO if you can get a real Merchant Account.

2checkout.com and paypal are both good companies, but only allowing one will limit customers.

Between the 2 I would say 2co. For some reason, customers doen't like paypal although it's a great processor. I think it's got to do with the bad name going around. Not that paypal is not secure, just that there are so many people using it that bad stories are bound to happen.