Considering that a great deal of civilian defense scenarios occur suddenly and at very close distances, carrying with an empty chamber could very well leave you vulnerable unprepared for many situations you would likely encounter.
I will dissent in the opinion that you will eventually get used to carrying a pistol with a relatively short, light trigger pull and pre-cocked striker like the M&P with a round chambered, because not everyone does and you very well may not. Plus, I'm still not convinced there is anything irrational about it.
I retrofit all my Glocks with NY trigger springs to more closely resemble the double-action revolver trigger I'm most accustomed to and comfortable with. I don't feel I need a manual with the NY trigger spring installed, but might if I stayed with the stock trigger. An M&P can be ordered with an optional 10 lb trigger pull as well as with a manual safety. I think a heavier trigger probably makes more sense than a manual safety since a lot can go wrong once the safety is off
http://smith-wessonforum.com/138849596-post18.html. Unintended discharges are a relatively routine occurrence during Force on Force training which simulates real world conditions.
At the range, carried securely in a proper holster, there probably isn't much to worry about with a standard, stock Glock or M&O trigger, but real world self-defense is so often chaotic, unpredictable with Murphy's law often injecting itself and a manual safety or heavier trigger can mitigate mistakes and misjudgments and keep them from turning into catastrophes.
"If carrying a gun like a Glock, which does not have a manual safety per se, and do not have access to a holster which covers the trigger guard(as is strongly recommended by the Glock factory), and have to shove the gun into my waistband, I'll make make sure the chamber is empty."
I think carrying with a round chambered is ideal and a heavier trigger and/or manual safety makes sense if it helps you get there, but I don't agree with the sentiment that a weapon carried in condition 3 is worthless.
The Thinking Gunfighter: THE MYTHS OF THE ISRAELI METHOD OF CARRY, or why carrying chamber empty isn't so bad.