For what it’s worth, I believe that if you truly want a launch day iPhone then you need to order directly through Apple. Every year there are a lot of people who complain about delayed phones ordered through Best Buy and the carriers, but if Apple says that you are getting a launch day phone then you are almost certainly getting a launch day phone. Of course there are always a handful of people who order through Apple and don’t get a phone due to shipping issues or whatever, but far far fewer than people who ordered from third parties.
A few years ago I saw a post that explained why this is the case. Apple makes the phones, so they know exactly how many they have and how many they can sell for launch day delivery, but the third parties don’t. They rely on Apple to provide the phones and apparently they don’t even know how many they will get. They could order, say 20,000 phones for launch day and base their preorders on that number, but when the phones arrive they might actually only get 10,000 because Apple didn’t have that many allocated to third parties. And that means that some of their preorders are going to be late.
