ShopThe short answer
Choose Q if you'll use passphrases or QR.
Q has the large color display, full keyboard, QR scanner, AA battery power, two MicroSD slots, and on-device multisig setup tools.
Choose Mk5 if you want the pocket signer.
Mk5 is smaller, lower cost, and excellent for MicroSD PSBT signing. USB-C and NFC make it a good fit for travel, multiple signers, and Nunchuk-style tap workflows.
Decision table
| Need | Better fit | Why |
|---|---|---|
| Typing passphrases often | Q | Full keyboard avoids cycling characters on a numeric keypad. |
| QR signing | Q | Built-in scanner and screen for animated PSBT QR workflows. |
| Small travel signer | Mk5 | Credit-card-like form factor with MicroSD, USB-C, and NFC. |
| Buying multiple devices for multisig | Mk5 | Lower price matters when each key gets its own signer. |
| On-device multisig setup | Q | Q can build and verify multisig configurations on the device. |
| Power isolation | Q | AA battery operation keeps signing away from a computer power connection. |
| MicroSD file workflow | Either | Both support PSBT signing over MicroSD; Q adds a second slot. |
You can switch later.
The seed is not tied to the model. A BIP-39 seed created on one COLDCARD can be restored on another COLDCARD model. Still do a recovery drill; switching models is not a backup plan.