First off - if your view is that breaches are inevitable (which is not unreasonable), hot wallets are a significantly bigger target.

Second - if ledger or trezor were breached, an attacker could come to your home and steal it. You’re either done right then and there, or you have a backup that you’re fully reliant on. Multisig fixes this.

In the worst case scenario for unchained, they lose every private key - you STILL don’t have a single point of failure, you can easily recover funds, and the attacker can’t do anything with the unchained keys. Not only does that make them less of a target, it makes them a futile target.