In terms of an attacker trying to brute force a 12 word seed or a 24 word seed with 12 words known, jerry0 is correct though.

A 12 word Electrum seed with no known words has 132 bits of entropy needing brute forced.
A 24 word Ledger Nano seed with 12 words known has either 132 or 124 bits of entropy needing brute forced, depending on whether the checksum word is known or not.

There are other differences in regards to derivation path and so on, but broadly speaking, they are comparably difficult to brute force.