Im thinking purchasing from amazon gives more support for the first month anyhow being that you can return it if defective...I would imagine if you have a hardware problem oculus will snail mail you email support while amazon there is no waiting or a replacement..
I'd buy direct from Amazon, they have a better return policy and much better logistics. Aside from that you have the warranty through Oculus. I have no idea what "full support" an amazon customer is not getting that an oculus customer is getting from facebook, I don't think there is a difference.
I always go with my Amazon Prime account, for the return policy. You will still get the same support from Oculus after the 30 days AFAIK, at least while in warranty.
I thought my first Rift S was defective, so submitted a return for replacement with Amazon. Well they shipped me a no charge replacement the next day via 2 day, and gave me 30 days to return the original purchase. Now that is hard to beat.
I typically like to order direct from the source (whether manufacturer or developer) rather than a 3rd party so I can support the creators. You'll get the same warranty either way, but Amazon is better about "no questions asked" returns (but don't abuse this or they will flag your account if they see you are pulling a "try before you buy" on them).
Oculus Direct for me. Although not advertised, the Oculus Store is good for refunds on purchases up to 30 days. I know because I had no problems getting my Rift S refunded after a few weeks use. Also good to have Customer and Technical Supports under one roof imho.