Assuming you want to carry .357 Magnum, I would probably go with the 66, especially if you can get the 2.5-3" barrel length.

The 60 would be easier to carry, but more difficult to shoot with magnum ammo. Of course, that depends on your skill and experience with shooting small magnums. Some people can do it all day long, some can't.

The 686 would be the easiest to shoot, but more difficult to carry and effectively conceal (I'm presuming you meant concealed carry). It can be done, no doubt, but you'll definitely have to pay more attention to your belt, holster, wardrobe, and body type/shape to find a combo that'll work.

The 66 is "just right." Easier to shoot than the 60, easier to carry than the 686.

I carried a 3" 65 IWB for a while, sometimes for 12+ hours, without a problem in terms of concealability and comfort. Easy to shoot, especially since I typically carried it with either mid-range magnum ammo or .38 Special FBI loads.

My only experience carrying a 686 was as an armed guard in an exposed duty holster on a heavy Sam Browne duty belt. Not bad at all when carrying for a full shift, which could run from 8-16 hours. I wouldn't want to try that with a concealed carry rig, though.

Now, if you want to stick with .38 Special, I might be tempted to go with the 60 (well, the 640 or 649 as I prefer either concealed or shrouded hammer J-frames) for better concealment but can still be shot well.

Just my opinion.