I wish S&W would bring back the 646 in a 3" barrel, with a Stainless Steel Cylinder, a pined front sight, and a Pro Model without the Loc. Smith & Wesson seems to quit on some new models a little too quickly. This was a good example.
I have owned a 610 for 20 years. I also own a 310 Night Guard, and conceal carry it in my rotation.
I like the 40 S&W cartridge. I like Moon Clips, and I also like the L Frame S&W revolvers. I would buy a 646 as described above at a reasonable price.