The difference is that Mixin Safe is supposed to be custodial. If that's true (which I haven't been able to verify) it shouldn't be affected by the hack.
Why wouldn't it be affected by the hack since it is custodial and the Mixin network holds the keys and obviously stores them in the cloud, Mixin safe is custodial that's for sure, there is no private key or seed phrase to any "safe vault" that you create.