Why wouldn't you use multisig? I've been thinking of going multisig, but the only con I'm aware of us the technical complexity.
As a multi-sig user myself, the two main pitfalls IMO are:
  • Additional backup complexity. In order to recover the wallet from scratch having 2 of 3 seeds is not enough; you'll need all 3 public keys in the quorum.
  • Privacy. Due to the importance of backing up the public key set, you'll need multiple copies of this stashed away (ideally one copy alongside each seed backup). While an attacker cannot use the public key set to spend funds, they CAN see your balance. The same is true with collaborative custody models.
Basically it all comes down to the xPubs being a pain in the ass. It would be amazing if that went away and you only needed N-of-M keys to recover the wallet. Perhaps someone will figure that out one day.
deleted by author