us and china motherboard differences

Hi, I was thinking about changing my iphone 6s plus motherboard since I have a 16gb model and I wanted to upgrade to a 64gb one. I looked it up on ebay and aliexpress and turns out that aliexpress is where they’re cheaper and also with more reviews from people that already bought them. I’ve noticed that even tho they’re all about the same price, some of them are about 10$ cheaper and what they have in common is that they’re all from chinese iphones instead of the others american ones, they say that boy can be used in every single country and basically are the same, so my question is, are they really the same? or is there really a difference and i should buy the us one. Also if someone had a bad experience with aliexpress motherboards, please let me know. Thanks!