I usually carry a 2 1/2" Model 66, as it's ideal for a conceal carry .357 Magnum. It's light enough (36 oz) to carry comfortably all day long (provided you use a good IWB holster and double thickness belt). It's also heavy enough to be comfortable to shoot with full power loads (provided you use a decent grip). It's also readily concealable, provided you use a short enough grip.
However, I usually practice with my 2 1/2" 686+, due to the increased durability. I also carry it frequently, primarily because I added night sights. It's about 4 oz heavier and while it is slightly wider and taller it still fits most of my Model 66 holsters. The Model 66 and 686 feel the same in the hand, and there no practical difference shooting one or the other, assuming the triggers are comparable.
I opted for the 7 shot 686+ because it was available used in excellent condition at a great price, and I certainly don't mind having a 7th round.
I also have a Ruger Speed Six that I'll also carry and shoot from time to time. The Six series DA revolvers were designed to specifically address the durability and forcing cone issues with the K-frame .357s. Ruger used larger, heaver investment cast fire control parts along with a stronger frame that does not utilize a side plate, and a heavier forcing cone that is not milled flat on the bottom as it is in the S&W K frame revolvers. That flat spot at the 6 o clock location results in the forcing cone being thinner there and the v shaped cuts caused by forcing cone erosion can create enough stress in that thin section to cause a crack.
They Six series DA revolvers hold up extremely well to a steady diet of .357 Mag loads, and the 2 3/4" barrel on the Speed Six is a little more efficient than the 2 1/2" barrels on my S&Ws. The Ruger trigger feels a bit more mechanical than the S&W but in general the trigger pulls are comparable (and like the S&W triggers of that era, they vary a bit from revolver to revolver).
The Speed Six also splits the difference weight wise between my 686+ and Model 66 at 37.5 oz.
2 1/2" Model 686-5+ (top), 2 3/4" Speed Six (middle), and 2 1/2" Model 66-4 (bottom).
In terms of longevity, I'd actually recommend the Ruger Speed Six, Security Six or Service Six revolvers. They have heavier forcing cones and while I have seen some very high round count Rugers with seriously eroded forcing cones, I've never seen one with a crack in it.
Otherwise, any of the L frames will do just fine. I don't really have a preference between the 686 and the 686+. The offset notch in the cylinder was actually a big marketing thing for Ruger with the Six Series revolver long before it showed up in the 7 shot 686+. It does remove what is otherwise a weak spot in the cylinder, but it's not something that will ever make a difference if you're staying within the 35,000 psi SAAMI specification, so it's mostly a marketing ploy.