It costs less to make a plastic frame than it does a metal frame, which means the plastic guns can sell for less. (I've been told during one of my Glock recerts that a new frame pops out of the mold every 85 seconds, and during a S&W 3rd gen recert that it takes a little over 30 minutes for a CNC machine to make a 3rd gen frame. CNC machine time is costly.)
I remember thinking that it was funny how some folks complained about the chunky Hogue grips on the CS series when the guns were introduced. Why? because I was originally told by folks at S&W that their marketing surveys indicated the rubber grips were preferred by owners, so they felt it was more attractive to have them come with the guns as "stock" grips. (Which just goes to show how you can't ever please everyone.
) Also, the factory felt the increased felt recoil in the smaller CS guns might put off some shooters, so they asked Hogue to design the grips for the new series to help reduce felt recoil.
I've always found the stock Hogue grips on my CS9 fits my hand as if made for me (and I only have medium-size hands, despite what some glove makers may think).
Yes, it has more palm swell than my 3913 equipped with the flat Hogues ... but I find it very helpful, as it also allows for a bit less movement of the CS9 in my hand, especially when my hands are wet (rain or sweat) or just really cold.
The CS45 grips are a bit fatter, or chunkier, than the CS9's ... until I start doing a lot of fast-paced shot strings, at which time I find the CS45 Hogue grips keep the gun perfectly still and locked into my grip. It's like they're glued to my hand, regardless of the loads I'm using or how fast/slow I'm shooting. The extra bit of felt recoil mitigation is handy, too.
Once I'm done actually shooting, and take the time to consider and "feel" the grip again, it once again feels a bit fat & chunky, just being held in my hand. Not the same as when I'm engaged in shooting the gun.
The CS9 also seems to have its "balance point" located more rearward in my hand (shorter slide). The faster cycling gives a bit more of a 'snap' for recoil (with a little more muzzle rise), but it also seems to put the slide/sights back 'on-target' faster than when I'm shooting my 3913. It makes for what I like to call a 'fast & lively' balance when shooting, regardless of the loads I'm using at the time (which have included standard pressure, +P and +P+ loads, depending what was being issued at the time).
As far as inherent & practical accuracy? I found I could shoot the CS9 every bit as accurately as my 3913. The small main spring & stirrup may give the trigger a little different feel (as the medium main spring/stirrup of the 3913 may give a different "feel" to some shooters compared to the large ones in 3906/04), but it doesn't seem to lack for practical accuracy. Evfen back when I was first just borrowing another instructor's CS9 (thinking about ordering one), I quickly discovered I could use it to shoot "minute of wooden clothespin" (on the target backboards) at 7-10 yards with it, much the same as I could using my 3913.
Between the CS9 & CS45 that I've owned and used for some years, if I could only keep ONE of them, it would be the CS9, hands down.
I miss that S&W dropped commercial production of the excellent CS 9's & 45's, and I hope they eventually devise something of similar size in the M&P series at some point.