Which is more private: Monero or Bitcoin via Lightning?

A recent post by an anonymous SMS service on X sparked a debate about private payments:
Which payment method offers better privacy - Monero or Bitcoin over Lightning?

Here’s a summary I think will be useful for anyone interested in private crypto transfers. And I know many clients of rabbit.io are.

Sender information:

• Monero: Permanently recorded on-chain as a list of 16 public keys (15 decoys + 1 real sender).
• Lightning: Nothing is published to the blockchain. Sender info is encrypted.

Recipient information:

• Monero: The recipient’s address is visible to the sender.
• Lightning: With proper routing setup, the sender may have zero knowledge of who the final recipient is.

Transaction amount:

• Monero: Partially hidden - the amount is concealed, but the fee is visible.
• Lightning: Fully hidden. Neither the amount nor the fee appears anywhere on-chain.

Transaction fingerprinting:

• Monero: Transactions can be distinguished by fee size, number of inputs/outputs, and known decoy keys.
• Lightning: Encrypted and padded to a fixed size (1300 bytes) - cryptographically indistinguishable from one another.

Routing control:

• Monero: No control over the path your transaction takes.
• Lightning: Payments only flow through channels you’ve opened yourself. You can avoid untrusted paths.

Privacy by default:

• Monero: Privacy is enforced at the protocol level, but some wallets may leak metadata (like IP addresses).
• Lightning: Privacy is optional - it requires careful setup and trusted channels.

My takeaway:
Monero offers solid privacy by design.
But Bitcoin, especially via the Lightning Network, is evolving - and in many ways, it’s already ahead.