Not sure what you mean by cryptographic strength - they are both Unique ID generators, not meant for anything related to cryptography.

UUIDv7 has 62 bits of random data, ULID uses 80 bits, so if anything ULID is "stronger" (meaning less chances of generating the same id within the same millisecond)

UUIDv7 has 74 bits of randomness, not 62, you forgot rand_a portion, so the difference is just 6 bits and only matters within the same millisecond.