Amazon for me all the way (and I'm not even in the US but in good ol' Europe).
I had a problem with my first M2P, filed a replacement and it was send (as usual) before I handed in my faulty one.
Customer service is excellent for my at Amazon - not sure how DJI treats it, but especially for such cases, I've always been treated superior to any other shop here in Austria.
It's best to buy from DJI directly or from an authorized DJI dealer. I keep a list of daily Mavic 2 deals from DJI, Amazon, and other authorized DJI dealers here: