The rule of thumb is that the tax ID you submit has to match the bank account the money is being deposited in. So if you're linking your direct deposit to a business banking account or want a check made payable to your business name, you should click 'Business' in the tac details of your Songtrust account. However, if you want your earnings to be deposited into your personal bank account, or have a check written to your name, you should choose 'Individual'. If you are international, you should fill out a W8-BEN as an individual, or a W8-EN-E for a business. Both can be found on the right hand side of the Tax Documentation page in your Songtrust account.
Essentially it is the difference between your earnings being payable to yourself or to your business. (For example, in my case it is the difference between payments being made to "Asia Smulders" verses "Smulders Publishing LLC".