One downside of the passphrase compared to a 2/3 multisig is you don't have any redundancy. If you loose your passphrase, you loose your Bitcoin. In a 2/3 multisig if you loose a sig you don't loose your Bitcoin.
You did a great job listing the pros of a passphrase, just wanted to throw out the con I thought of.
100%
Personally I roll with multi-sig these days but it took me a while to upgrade from single-sig + passphrase.
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