The decocker is always able to be fired by pulling the trigger....the decocker function lowers the trigger to essentially a half-cocked, really more like three-quarters, position mechanically......where as the safety version you can lock the trigger so it can't be pulled. The safety version can be "decocked" by holding the hammer when fully cocked, pulling the trigger and manually lowering the hammer. Personnally, I prefer decockers, many prefer safeties......it really just comes down to preference. I've never been one to trust "safeties" to actually keep me safe especially after working on them and seeing how they can fail. A decocker in essence is like a revolver, its always ready to shoot...just pull the trigger, the first round is DA...then the easier SA