I have a number of Smith & Wesson revolvers and I really, really love them all and I shoot almost every single one of them on a semi-regular basis, so I have a decent amount of hands-on experience and my opinions reflect those experiences.
If I'm shooting .38 Special, there is no other S&W that feels more "RIGHT" than a K-frame, and if I'm going to define it further, it's probably going to be a 4-inch heavy barrel K-frame, like the Model 10 or 64. If the task is to shoot 400 rounds of .38 Special and hit my targets to the best of my ability, it's probably going to be that, although a 6-inch K-frame is probably right behind. I don't have nearly as much trigger time on my 6-inch Model 66 just quite yet.
If I'm doing mostly .38 and I want the option of .357 on a rare basis, a K-frame magnum is a fine choice. The Model 19, 13, 65, or 66 will be a great and versatile handgun. And I would consider myself not NEARLY as recoil sensitive as many folks that I know, but I can say truly that .357 Magnum from a K-frame is not comfortable and for me, it is NOT an all day affair. One box is plenty, frankly.
The L-frame does handle the magnum ammo better, both for the longevity of the revolver and the shooter, and for comfort, the added weight helps a lot. But I only have one L-frame and it's a six-inch 686, and there's a LOT of weight out front and the balance on this revolver is simply not there. I have a hunch that a four-inch L-frame would balance far better, but on a range day where I'm shooting 3 or 4 boxes of ammo, my six-inch L-frame is tiring by the end of the day with all that weight out front.
Enter the N-frame. Mine is the FAR more plain version of the beautiful Model 27, I have a Model 28-2 with a six-inch barrel. And when it comes to shooting the heaviest handloads that I build, no revolver I own handles them better and more comfortably than my Model 28. Full-boat .357 Mag from my Model 28 is pure fun & enjoyment to me. I have only one true complaint about my Model 28, and that's the fact that the big cylinder heats up and seems to take forever to cool and I end up burning my hand while ejecting brass because it's so much fun that I don't want to put the revolver down to cool off.