Ellasman,
As I understand it, the decocker only is a spring loaded affair, like on a Sig. You use it to decock the piece, and it springs back to the ready position. There is no "safety" feature on this type of gun. The decocker/safety is not spring loaded, and when you use it to drop the hammer, the hammer cannot be cocked until you manually raise the lever. Even if you work the slide, the hammer will fall on the block if the decocker/safety is down.
To me, the only safety that really counts is between your ears. The more levers and wizzie gizzies you hang on a gun, the less I like it. Presuming you practice safe handling technique, the safety on a double action semi-auto is just one more thing to remember/get in the way when it counts. I'd opt for the decock only lever.
About the only time that I can see a safety on a double action coming in handy is if someone gets the gun away from you, and is not real clear on how it works. That may give you a couple of extra seconds to rectify the problem.
