Bitcoin and Monero, Monero preferred.
Awazon accepts two coins, and the choice is simple.
Monero is the privacy default, the coin to use when you do not want the payment legible on a public ledger. Bitcoin is there for the vendors who only take it. The deposit address is fresh per order.
Default to Monero unless a vendor forces Bitcoin. If you pay in Bitcoin, do not send straight from an identity-checked exchange, because that ties your name to the deposit. Route through a fresh wallet or swap into Monero first.
Awazon