Transparent coin, private coin, which to pick
Both work on the market and both clear in the same way. The difference is what the ledger shows, and the choice is a judgement about who you do not want looking at the balance, not about which one is faster.
What the ledger shows
Bitcoin is a public ledger. Every transaction is on a chain that anyone can read, and a chain analysis company can follow a balance from a market deposit to a wallet with a fair amount of confidence. Monero is a private ledger by default, and the same transaction is a line that does not say who sent it or how much. The difference is not the speed, it is the reading.
The confirmation counts
The market credits a deposit after the confirmation count for the coin. Bitcoin, litecoin and bitcoin cash need three, which is a few minutes. Monero needs ten, which is around twenty minutes, and the longer count is the coin being careful, because a private ledger needs more than one confirm to be sure the coin is not double spent. The payments page has the table.
Which to pick for a first order
For a first order, the smaller amount is the safer coin, whichever it is, because the first order is the one that teaches the mechanics. The coin is a secondary decision. The habit that matters is the same for both, which is to move the coins out as soon as the order closes, because the coin’s privacy does not protect a balance that is still in the building.