This topic is certainly very interesting. I have been using, buying, collecting Smith and Wesson and Colt revolvers for almost 50 years. In that time, I have seen some pretty fantastic examples of quality in both firm's revolvers. I tend to be partial to Smith and Wesson and have, by far, more examples than Colt.
I have noticed that there were some examples purchased in the mid to later 70s that were not necessarily in the same category of quality of the pre-war era and of the post-war 50s era. My issue Model 15, built in 1972 was just exquisite..... perfectly timed and well finished. In fact, the finishes I noted on most of the Model 15s I saw, bought and used seemed to show exceptional finishes across the board. Some Model 19s seemed to be not as well finished as the Model 15s.
I noticed some rather gaping gaps in the fitting of the sideplates in many Models, even the Model 27, 29, and 57. One revolver though seemed to not have many of these issues and that was the Model 28, which showed rather exceptionally well fitted sideplates. I did notice that many Colt revolvers seemed to have some issue(s) with quality control and one Python I bought in/around 1977 had trouble getting the thumb piece to open, or closed to allow the cylinder to be opened or closed.
Colt was having labor problems with the Company and its work force during the 70s if I remember correctly. However, for the most part, I always thought that quality was always rather pretty good overall for both Smith and Colt. But, again, the thing that struck me most was the fit and finish of the Highway Patrolman. I have a few of them still and each time I look at them, I am struck by how well the sideplate fir and finish are so consistent.