Why Monero Matters
The coin you pay in is one of the few choices on a darknet market that is purely yours, and it is the one with the longest tail. Bitcoin is easy to get and easy to trace. Monero hides the amount, the sender and the receiver. If the reason you are on a darknet market is to not be traced, paying in a coin that traces you is a contradiction worth noticing.
What Monero hides
Ring signatures mix your transaction with others so the sender is not identifiable. Stealth addresses mean each payment goes to a one time address the recipient derives, so the receiver is not tied to a single public address. The amount is concealed by a commitment scheme. Together they remove the three things a public ledger exposes, and that is the privacy Bitcoin cannot give.
The practical trade off
Monero is slightly harder to source than Bitcoin and the fee is steadier rather than spiky. Neither is a problem for a normal order. The decision is not about convenience. It is about how much the trail matters to you, and for most people on a darknet market, the trail is the whole point.
A middle path
If you prefer to hold Bitcoin, you can mix it or route it before it reaches the platform, which breaks the chain. It adds a step, but it keeps the ease of Bitcoin with less of the trail. Whether that step is worth it is your call, and it is the only call that matters here.