[jsjenkins168]

Whether the attack is brute force or a time/space trade-off, longer salts increase addressable space which increases time or space required to achieve a collision. It doesn't matter how you're doing it, this is a simple fact.

A larger key is always more secure.

[thomasptacek]

The salt is public. If you have the password table, you have the salt. The attacker doesn't have to guess the salt with an incremental password cracker (read: almost any password cracker).

The mistake you're making is your misuse of the word "key". Larger keys are more secure. A salt is a nonce, not a key.

Can I say again that people shouldn't be rolling their own password scheme? This is a problem that has been well-addressed for decades, but the majority of new applications still ship with code that is inferior to public domain code from 1976.