The advantage of using Interfolio is that your letter authors will only need to submit the LOR once, and then you'll send it to every school you want. They're already taking time from their busy schedules to help you, and this way they don't have to make different letters for all your schools. Unless they really want to do that. You can always ask!
Personally, I just interfolio and then sent my letters from interfolio to AACOMAS. I chose to do this because then I could ask my letter writers before the AACOMAS application opened in May. I sent to AACOMAS because it was less maintenance for me. I sent them in once and then all of my schools got them. No extra work, no ambiguity as to whether they were delivered.