Because you are a cop, I dont like your trade. For civilian purposes, I would not argue with you at all. The difference is probability of actually having to fire the weapon, the civilian gun being much less likely.

I own a 642-2, which I carried for a long time without firing much. Once I started shooting it, it started making multiple trips back to S&W to correct problems that will only become apparent during shooting. For example, the gun would hang up after a couple of rounds fired, apparently caused by an excessively small barrel cylinder gap. This is the 2nd cylinder on this gun in less than 1000 rounds. If I were to buy another 642/442, the gun would have to prove to me that it is reliable before I would carry it. I now know the current one to be reliable from extensive shooting.

The Glock is reliable, easier to shoot and can put triple the number of rounds onto a target within 25 yards in comparison to the 642. The only way you have can put a similar number of rounds on target is to carry both the 640 and 642. The 642 can hit very well at 25 yards, if you take your time and aim very carefully. That is not what the gun is built for.

The one and only area where the 640/642 is superior is in safety from accidental diischarge, particularly when carried in the pocket rather than in a holster.

If you are going to have a 640, I prefer the +P38 Special, pre-lock 640 to either of the current lock equipped guns.