FWIW, when I only owned a late production 3913, I had little interest when the CS9's were released. I had a friend that bought one of them when they were only available in blue, in the early configuration (plastic sights, single side safety/decocker). I think he picked it up for something like $269-$279 (with a CS45 at the same time for the same price). I didn't shoot it, but I inspected it when he brought it to me. Seemed nice enough. Small. I remember thinking it was a big grip frame for a small gun (although the Hogue stocks were nicely hand-filling).
It wasn't until another instructor bought one and let me try it for a few range sessions (alongside my 3913) that I realized that it was a handy, well-balanced and surprisingly accurate little pistol. It easily rivaled the practical accuracy of my 3913.
The grip's fatter, more curved stocks and shorter slide/barrel gave it a unique balance in the hand. The weight was more rearward over my hand, versus the 3913's heavier slide putting more weight just forward of my hand. The stout little hammer spring and different grip made for a little different trigger pull, but not necessarily in a bad way. Just different.
The CS9 didn't seem to have any problem feeding & firing any of the regular ammunition in use for training and/or duty at my agency at different times, which included 147gr JHP, 115gr JHP/FMJ, 115gr +P+, 124gr +P & 127gr +P+. The felt recoil was a bit sharper than with the 3913, with seemingly faster cycling (less slide weight and a rather short, flat-wound recoil spring). Fast & brisk ... but with similarly fast return-to-target, and the Hogue grips stocks easily soaked up any felt recoil. No stinging in the hand.
The funny thing is that I'd originally bought a CS45 first (just because it was the smallest .45 S&W had ever made), and while it was a fine little TDA .45, the slightly fatter grip and the level of felt recoil in the CS45 didn't make it one of my favorite .45's to shoot a lot ... at first.
My original model 4513TSW enjoyed more range use for quite a while.
Sure, over the years I've subsequently lost track of the rounds I've fired through the CS45. It became a gun that I took to use when working range sessions simply because it wasn't a "favorite". I wanted to make it work as well for me as the larger .45's I used.
Once I'd picked up the CS9, though,
that quickly became the pistol I reached for when wanting to train/practice with a diminutive pistols that was an enjoyable & accurate range gun, as well as a light and easy-to-carry 9mm.
My 3913 started seeing increasingly less range time in favor of the CS9.
Over the ensuing years I've made myself pretty much rotate usage of the little 3rd gens, alongside the Glock subcompacts, as well as the excellent SW999c, so they all see a fair number of rounds as they're used for range sessions.
That little CS9 is still one of my all-time favorites.
I'd have a hard time choosing between the 3913, CS9 & SW999c if I were only going to keep ONE of the S&W's, though.
The SW999c has a better trigger and grip profile/ergonomics than either the 3913 or the CS9, but the little 3rd gen 9's are still about as close to state-of-the-art as anybody's ever achieved when it comes to a metal-framed TDA compact/subcompact, at least to my way of thinking.
If pressed, I'd suggest the 3913 is probably an easier gun for more shooters to use, while the CS9's lighter weight and slightly increased felt recoil might be better utilized by a more experienced shooter. Dunno.
Just some thoughts, since this thread is still going ...
I don't have the answer which is "better", though the CS9 or the 3913. You'll notice I still own BOTH.
