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.
True, besides of this SLIP39 is not a standard
(yet) for SSSS, (though,they try to make it standard ) and is not supported by most of HW from other developers. Thus should I have the opt between BIP39 and SLIP39 SEED phrases I would choose the latter.
(BTW, Foudation manufacturer of Passport devices argues that BIP39 12 word SEED phrase have to be standart for all HW).