I'm not sure how the actual weight compares but my 642 feels lighter loaded than my Shield 9. The 642 and the Kahr PM9 were about the same weight (at least feel wise) to my recollection, though I don't have the Kahr anymore.

CM/PM9
I carry mine in sweats and gym shorts with a smart carry whilst running, hiking, mountain biking, and have even take it mountain climbing up to almost 15k. I've also worn it under shorts with no shirt.
It's hardly noticeable that way but add a hybrid IWB holster and it all but disappears into a pair of pants

The XD-S 9 has been perfect...

I considered the CM9, LC9, Solo Carry, and the P938.  I bought the P938 because of the size and quality primarily.



Fits in your pocket perfectly.

I own a Shield and a Kahr PM9. Both are excellent firearms and completely trustworthy. The Kahr has roughly 800 rounds with only a few shooter related malfunctions-grip related. I'm on my second Shield, first with safety, second without. Both reliable but I did experience a couple stoppages with the first until I put a Talon grip on it. I mainly carry the Shield because of the trigger, as it's closer to all my other pistols. Based on your criteria, the Kahr is worth looking into. Just keep in mind that any gun that small requires a firm grip and that you keep your mitts off the mag release and slide lock.

My sister has a Solo CDP, it is truly the finest compact I've ever handled.  The ergonomics are the best of anything made.  However, it's all metal construction  takes it heavier than most.  I hate myself for not buying myself a CDP at the time.  Shoots great, has excellent reliability and is a sweet overall gun.  Too heavy for this purpose though.  

This is a hard decision, good thing I have time to compare.

The only gun I pocket carry is the S&W Bodyguard 380.  IMO it's big enough to grasp/shoot reasonably and still small enough to fit in a pants pocket.  There are smaller guns out there in both 380 and 9 but I just can't get a comfortable grip on them.  Also have the S&W Shield 9mm.  Love the gun as an EDC but it's a little big for the pocket.