To delete a customer, Transfer or Merge Operation in Party Merge?

 Hi,

We need to delete a bulk of customers.

Now as I knew, there is no way to do this. The only solution is to do Party Merge then Account Merge customer by customer.

Now what I need to know is in the Party Merge > Party Sites tab, the Operation can be 'Transfer' or 'Merge'.

Now what is the real difference between them and what should I choose to accomplish a full deletion of the customer.

P.S.: The default value is Transfer

Thanks,

Christine