The Model 15 ran for 50 years, 1949 through 1999. Now you can buy one again as a "Classic" model. That started a few years ago. That's how I bought my Model 27, as a "Classic".
A 4" Model 10 will work perfectly well. If you think you can shoot better with a Model 67's adjustable sights that is your call but I can assure you that a 4" Model 10 can do everything a Model 67 can do. Most of my Model 10s, and I admit to having too many (is that possible???

), are snubbies. But I do have two 4" Model 10s. One is a typical, old, beat up Wells Fargo gun. At ten yards it can take the eye out of a fly. The other is a heavy barreled, somewhat rare, .357 Magnum. Using .38 Specials I scored my first perfect score on the Texas license to carry test, 250 out of 250. It just takes practice.....