In my biased opinion (I owned a M19, the blued version of the M66 S&W), I think the Taurus is a better, stronger, more accurate gun. The newer ones have the transfer bar trigger which is very smooth and even the older ones use a floating firing pin which I prefer since I've had hammer mounted ones break.
Both my M66 Tauri are more accurate with .38 special loads than that 19 was and I appreciate that. My 4" Taurus is a genuine 1" five shot at 25 yards shooter with wadcutters. They're all about equal with .357 loads. The Taurus does NOT have the flat on the bottom of the forcing cone that the Smith does. the Smith is known for cracking the forcing cone in that area and I've seen that happen on a M10 before (a .38 special K frame). I'm convinced that the Taurus's forcing cone is stronger. I've seen Taurus guns that have fired many, many rounds of hot loads and were not loose. The Smith was noted for getting loose if hot loads were exclusively used in it. However, I must say that I've never seen a loose M19 or M66, well, not worn out, that was done in an unreasonably short time. I think those stories were from police arsenals where those guns were fired daily with many hundreds of rounds. I don't think the K frame is weak enough that I'd have to worry about wearing one out in my lifetime. I think the K frame's advantages in weight far outweigh any lack of strength when compared to L frames or the GP100 for carry. I don't really care much for the heavier GP100 or L frame guns. I like an easy to carry revolver.
Suit yourself, but I'm very happy with my M66 Taurus revolvers and have no worries that the K frame Smiths have been discontinued. You can't buy a K frame new anymore and I'd MUCH rather have a new M66 Taurus than a used K frame. If I can get a deal on a used stainless M66 in the future, I'll add it to the arsenal and have one in blue, nickel, and stainless.

I gave $180 for my 3" older M66 and $200 for the 4" newer one. You can hardly buy a BARREL for a K frame Smith for that kind of money. Even a clapped out old used M66 Smith would run you $400 down here at a gun show. To me, it's just a no brainer. I've owned and fired both and the Tauri I own are better shooting guns, so why would I swoon for another Smith? I still have my old M10 for my Smith and Wesson fix, and that old gun, built in the early 60s, was made at the zenith of Smith and Wesson craftsmanship. Modern Smiths, IMHO, don't compare.