LND is an aezeed wallet using BIP84 key management (24 words).

Aezeed is the mechanism through which the private keys of a LND node are derived from a seed phrase. Unlike other popular seed phrase formats, it allows for versioning and wallet birth dates.

LDK use a BIP 32 extended key (12 words).

I don't know exactly why LND choose to use aezeed format (24 words).

But the difference in security between 12 or 24 is insignificant in this matter. Is only about the keys system they use.

bitcoin_beginners

Zeus quick guide: migrate node to new LN implementations

DarthCoin

LND is an aezeed wallet using BIP84 key management (24 words).
>Aezeed is the mechanism through which the private keys of a LND node are derived from a seed phrase. Unlike other popular seed phrase formats, it allows for versioning and wallet birth dates.

LDK use a BIP 32 extended key (12 words).

I don't know exactly why LND choose to use aezeed format (24 words).

But the difference in security between 12 or 24 is insignificant in this matter. Is only about the keys system they use.

Maybe this document can help more:
https://github.com/lightningnetwork/lnd/blob/master/aezeed/README.md