I think that using a partial range of motion is more beneficial, especially in regards to the bench press. Obviously if you are a powerlifter and this is necessary to complete a lift then you are in a different situation.
However for a bodybuilder, you want to be working the chest when you bench press. If you let the bar drop all the way to touch your chest then you are just hurting your shoulders and not working the chest muscles.
Furthermore, I wouldn't even recommend locking out your elbows as this can be bad for your joints. Others may view this as "cheating" because you don't go all the way down, but if you have a bigger chest and less joint pain.... well I think that speaks for itself.