Ah, you look for the rates alone and ignore many of the other important points. Some reps will sell you a merchant account with a bank that isn't Internet knowledgeable. They may even have you set up on a watch program that will freeze your funds when a sudden surge of activity shows up. Maybe your web site makes someone's 'hot site of the day' list or is mentioned in a magazine and your page counter hits the billions and orders come streaming in.
Some merchant accounts require a separate checking account with the sponsoring bank.
They won't let you use your own checking account. Second, consider when those funds become available to your business. Typically the credit card funds are deposited into this account within two business days. Then you have to write a check to yourself to get them into your business checking account, another two to three business days. So, maybe it's a week later when you finally can use those funds.