My mistake:
Condition 0 - A round is in the chamber, hammer is cocked, and the safety is off.
Condition 1 - Also known as "cocked and locked," means a round is in the chamber, the hammer is cocked, and the manual thumb safety on the side of the frame is applied.
Condition 2 - A round is in the chamber and the hammer is down.
Condition 3 - The chamber is empty and hammer is down with a charged magazine in the gun.
Condition 4 - The chamber is empty, hammer is down and no magazine is in the gun.
This being said, Condition 1 is safer than Condition 2. Obviously nothing in the chamber is safer than having a bullet chambered.