I have two of the older 6 shot 66s and they are FANTASTIC revolvers compared to anything out there. I absolutely LOVE the 4" nickel, unreal accuracy for a medium frame 4" gun and a good weight for carry in the field. The 3" totes IWB very comfortably and is, itself, an accurate gun. These revolvers are simply under-appreciated in the gun world what with all the Taurus bashing that goes on. I owned a Ruger Security Six and a M19 Smith and traded both off, but my 4" 66 is definitely a keeper and I'll probably hang on to the 3", too, though I kinda prefer my SP101 for carry, a little easier to tote if I'm not quite as accurate with it due to a shorter sight radius. But, the little SP101 is plenty accurate enough!
I have simply never fired a 4" medium frame DA .357 revolver that can match that 4" 66 for accuracy, though. Accuracy counts in my collection. It's also a very tight, rugged, revolver for carry. I'd kinda prefer stainless, but nickel is pretty corrosion resistant, you just have to carry it in a good, padded holster to keep the wear down. I carry it in a flap style padded cordura holster in the field.