I would suggest you consider this a good learning experience. You will face this question hundreds of times in your life as a programmer: Which method is best x or y? So accept that you're not always going to be able to turn to your co-worker and ask them for the answer. You're going to have to start doing some of your own empirical testing one day. And this is an easy one to practice those skills on.
Make up a quickie little test form that copies a 10 gig directory filled with a few thousand files from A to B with a timer running using method 1. Then that same source directory A to C using method 2. And again from A to D using method 3.
Not only will you get comfortable doing your own testing and confirmation but you'll learn 3 different ways to code for the same need.