I own several Model 66s and 686s but like the K-frames better. I bought a six-inch 66-2 ten or so years ago for $400. It's my favorite target revolver since I added a Millett rear sight and target hammer and trigger (flash-chromed parts are harder to find than color-case hardened). I've often thought about returning it to S&W to have the integral front sight replaced with a Patridge but hate to alter it in a non-correctable manner.
Ed
Your post struck a nostalgic chord for me Ed.
As a brand new Cop, we had to purchase our own guns and leather. I got a S&W 66 No Dash 4" from my Road Captain that he had had tuned. He substituted CCH parts as flash chromed TT/TH were very hard to come by. I carried it for years and years until I foolishly sold it after retirement.
Many years later, local pawnshop, and voila...THERE IT IS. Except it wasn't, but it was set up identically to my uniform duty gun from years past. And I mean identically set up, down to the amazing trigger job on this one. This one will never be sold and is one of the most accurate handguns I own (and I own more than a few) Perhaps it's muscle memory, perhaps ergonomics, perhaps the tuning...perhaps all of the above, but it's my old friend back again, this time for good.
So yeah, the Ls and Ns are heavier duty (and heavier), but for all day comfort and ease of shooting with more inherent accuracy than most mortals possess...the K stands for King imo.
Target is from end of my first outing, 2 cylinders full plus 3 remaining rounds, at 30 yards...with my now 60 year old eyes. So yeah...KEEPER.
(at 22 yoa I was a BMF with a S&W

, group would have been 1/2 the size, but...getting old, whadda ya want?)