The benefit of using a USB connection is that every time you connect your Trezor device to your computer, it will undergo a firmware hash check. See https://trezor.io/learn/a/trezor-firmware-hash-check
The advantage of keystone is that its screen is large, making it easy to check payment addresses or contracts, and prevent clipboard viruses. It is also difficult for online viruses to infect hardware wallets through QR communications. The disadvantage is that Keystone cannot check the firmware of the hardware wallet and the authenticity of the device online in real time. Therefore, in addition to device authenticity verification, Keystone is also designed a self-destruct function. Its defense focuses on supply-side attacks.
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