Authorize.net is not a merchant processor. You would have to get both Authorize.net and another processor to compete with WorldPay. Auth.net charges around $20 per month and 10 cents a transaction. This is on top of any rates that you have to pay to your merchant processor.
WorldPay Payments guarantees to match or beat ANY rates offered by other merchant services. This means that no matter, if you choose a merchant provider other than Mercury Payments, your cost to use Auth.net will be $20 a month and 10 cents a transaction more.
All companies are in business to make a profit. Please make sure that you fight hard to get the best rate possible while shopping around and forcing WorldPay Payments to match or beat the rates.
USE ON ECOMMERCE AND CARD PRESENT:
Technically you are able to use Authorize.net or WorldPay Payments on BOTH Ecommerce and Card Present transactions. Card present is used on Point of Sale or Event invoices where the customer is present with card in hard.
The use of Authorize.net is done at the users own risk due to a low level of security offered through Authorize.net. See Security below.
In early 2016 PCS upgraded it's WorldPay Payments integration to include P2P or E2E encryption. P2P stands for Point to Point and E2E stands for End to End. They are the same security that protects the card holder data from End to End assuring no criminals are able to capture card holder data during the transaction.
Authorize.net has NO advanced security protecting card holder data and it is not recommended to be used.
WorldPay Payments offers to be the best deal for you while providing the best security and reducing the liability.