If you can, use multiple.
At least compared to a single backup, your bitcoins can still be safe in case one of the backup is compromised.
I meant that a single-share backup of 20 words has no advantage over a backup of 12 words.
Okay, in that case, its minor advantage is its higher checksum bytes of 30bits compared to BIP39's entropy ÷ 32 bits (
12words: 4bits or 24words: 8bits).
Yes, very minor since single backup isn't really the main reason for using SLIP39 anyways.
As for compatibility in case it has to be imported elsewhere, that was only an issue during its early adaptation,
But now, its fairly easy to find a tool or wallet that can restore SLIP39 mnemonics (
not that it's recommended).
BTW,
Our fourth word is: leader, which means the total number of secrets can be 3.
If the attacker it tech savvy, he can decode the SLIP39 mnemonic to bits to see how many required mnemonics and how many backups you have.
That information is certain unlike judging just from the word which is a representation of a 10-bit segment.