Addition/Deletion records based on method argument
Performance wise you're not going to notice the difference.

There is a far better solution available to you though. That is to have 2 separate methods altogether.

You already have a switch statement before calling the method in which you know that it will be a delete or an add. This makes it really easy to just call the right method.

Having separate methods that each do a specific thing makes the code easier to read and maintain later on.